Motorstorm: Arctic Edge was developed simultaneously for PSP + PS2. The versions only released 1 month apart. Same with Jak & Daxter: The Lost Frontier.

I understand where you're coming from, because there was a huge list of first-party IP's which got ported from PSP to PS2. The majority of them (Ratchet & Clank Size Matters; Secret Agent Clank; Syphon Filter Dark Mirror) appeared on PS2 within a year of releasing on PSP. Same with the GTA games & Silent Hill Origins.

Point I'm trying to make is if it was going to happen, I think we'd have heard about it by now.

There were some exceptions to the 1-year-porting rule (Syphon Filter Logan's Shadow; Twisted Metal Head On; WipEout Pulse), but the catch with all of these is they were all a regional exclusive (the first two were NA only; WipEout was EU only).

Only situation I see it happening is much further down the line if there's another Uncharted Vita game and they eventually get ported as an "Uncharted Origins Collection" (i.e. God of War).

I think it's kind of unlikely though. I'll probably get ripped to shreds for saying this, but despite Sony's much-worse-performance with Vita compared to PSP, I feel like they're doing a lot more things right this time around regarding games. Exclusive IP's only on Vita (Gravity Rush; Soul Sacrifice; Tearaway) are a good first step, and I'd hope that as a result of this learning they'd also realise that porting their handheld-only titles to home consoles is not a good move in any way (diminishes value of the handheld console itself and won't get stellar sales from home console versions of the games anyway).

I'd also say that personally, I wouldn't buy home console versions of Vita games I own anyway. I have Jak: Lost Frontier; Secret Agent Clank & Syphon Filter: Dark Mirror on PS2. You can tell they're handheld games. I have had fun playing with them, but I'm actually quite tempted to sell them and buy the PSN versions to play on Vita instead. They were designed to work on handhelds and it just comes across if you play them on home consoles. But, that's just my own personal opinion and ymmv.

Not likely for PS3, maybe PS4 but the PS4 will have both franchises anyway (killzone is already announced) so there is no point

Not yet. Maybe in the future, for the PS4.

Vita is still in dire straits, last thing it needs is losing the few exclusives that are a reason for people to buy one. ie. Uncharted GA, Gravity Rush, Soul Sacrifice, etc.

Vita has already too many PS3 cross games.

Neither will happen.

I hope this never happen because this could weaken Vita

Unless Sony wants to drive more nails in to that coffin I doubt this will happen.

If it were to happen though likely after Vita gets discontinued though I doubt Sony would actually do that.

If SONY does that I'll likely just give up on them when it comes to the Vita. Really hope they don't do that.