It's probably more of the opposite. 

FF7 Remake and Dragon Quest XI are already underway on Switch using Unreal Engine 4, the Square-Enix president wanted more games for the system, so now the Final Fantasy XV team is looking at taking what the other SE teams are doing on Switch on Unreal Engine 4 and trying to adapt to their game. Kingdom Hearts III I think is already a done deal on Switch too, they just want to finish the PS4/XB1 versions first. 

Maybe it will be a hybrid engine, using the best tech from UE4 and Luminous Studio.

The Switch has an even weaker CPU than the PS4, that means that the games would have to lose polygons and perhaps some graphical features.

Final Fantasy being away from Nintendo consoles for 23 years is absurd. It's time for that to end regardless of what XV itself is. 

I don't know what kind of voodoo magic you think is in Final Fantasy 15 that would make it not runnable on a switch when the last system contained XCX.

 There are very few games released this generation that need PS4 power to exist. You're just prettier last GEN games.

Problem with FFXV is very demanding Luminous engine, so game doesnt run good even on PS4 Pro, so porting game in UE4 engine for Switch would work because UE4 engine works great on Switch.

You're partially right and wrong. While FF has been beaten by games like DQ, and other series like Pokemon, Animal Crossing, Splatoon and Monster Hunter are more consistent in sales... FF is still a tier 1 game in JP. JP might be more jaded to it now, but thats yet another reason why it should be on a handheld.

MH has not fallen in popularity. They just milked X too hard. (The PSP games are way overtracked, the 3DS games outsold them)

If SE continues to handcuff the mainline series to traditional consoles, that will no longer be the case in the future.   While the series has maintainted consistent worldwide sales, its been trending downwards in Japan ever since Final Fantasy VIII with FFXV being the slowest selling mainline, non-sequel Final Fantasy since FFV over there.  The Switch and its skyrocketing sales in Japan seems like the way for SE to keep Final Fantasy relevant domestically which is why they're probably looking for a plausable scenario to put FFXV on the hybrid.   I wouldn't be surprised if FFXV on the Switch is signficantly more important ot SE than it is to Nintendo.

Getting almost 1 million physical sales on a console in Japan is definitely tier 1. It's just that the tier goes from 1 mil to around 1.5. Splatoon is a rare game that might even go past that though. 

I'll admit that immediately after writing that I checked again and realized I was wrong. However, I had a nap to get to Still, I don't think the snarkyness was really necessary. 

Infact, it only takes a quick glance to realize why this is misleading and also why it's a terrible argument. Monster Hunter Freedom 3 did NOT have a successor, or an updated version. It was the last MH released for the PSP. Taking a quick look at the sales of the Monster Hunter series makes it quite obvious what the truth is.

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The series hasn't declined in popularity, the games sales are just split up between rereleases. It's like considering GOTY editions as different sales. Like look at Monster Hunter Portable 3rd, it had no rerelease or sequel. Monster Hunter 4 on the other hand sold 6.7 million copies in just japan alone. Monster Hunter X sold 5.9 million. I mean a port of a Wii game sold more then half an entire generation of Monster Hunter games on PSP ... 

The series isn't "less popular", it's just that the 3DS entries have multiple iterations, and the new games have been handled terribly. Generations on Switch will probably sell 600k lifetime, but that's not a sign of a less popular franchise it's a sign of literally selling the same game 3 times. Monster Hunter World will probably sell 1 million on consoles in Japan, that's not a sign of wanning popularity it's a sign of making a game for a different audience. 

Even if Portable the 3rd was the best selling though(it isn't), going down from a peak moment in a series isn't losing popularity it's having stability. Every series at some points has a peak it won't reach again. That doesn't mean it's less popular it means the stars aligned on one title. In fact the series has more consistent average sales per release anyways. 

This is all extremely off track but I just think that comment had so many holes in it it bared mentioning. In the end of the day FF is an A tier series in Japan at least on home consoles, it might change in the next 6 or so years but it is still an A tier series now. I don't think FF15 is the most important support for the switch though, and ultimately all we can do is wait and specualte I think KH3 and FF7 Remake are more important to be frank.

For the "tier" conversation, we just have very different parameters for a top tier series. The style of game has  

They are separate games, separate SKUs. You don't get to combine them together to invent a way to say that MH hasn't declined in popularity. Not to mention that MHP3rd was given an HD port on PS3 that did over 500k, but that doesn't really matter. It doesn't get combined and Monster Hunter Freedom 2 and Monster Hunter Freedom 2G (Unite) doesn't get combined. Every single entry in the series has seen a port, re-release, or expansion. The 3DS has no more re-releases than any other platform.

If we can't agree on this, then not much can be gained from going forward lol.