I know we all crave originality and new IPs in gaming, but most of us likely have a yearning to see the return of past franchises that have not seen a new release in quite some time.

When do you consider a franchise dormant? How much time has to have passed since its last release?

For me if a franchise skips an entire generation of consoles without a new release of some kind I take it as a bad sign. Perhaps that franchise is no longer active.

I also don't think we are prone to seem much revivals as we used too. I can think of dozens of gaming IPs from yesteryear that I think deserve another shot and to be resurrected.

Rayman comes to mind. Origins and Legends were excellent yet we never got another game.

Then again GTA did not release a new entry on the PS4/Xbox One generation, instead remastering GTA V and exploiting GTA Online for all its worth.

Metroid Prime hasn't seen a new game since the Wii. We know they are working on 4 but haven't seen anything of it. The remastered the original Prime game last year though. Some suspect Prime 2 and 3 will also be remastered at some point. Unexpectedly the 2D Metroid series was revived during the wait for Prime 4.

So what franchises are dormant for you and which are just caught up in a long dev cycle?

I would say roughly a console gen (or 5-8 years) is pretty fair.
15 years or more is dead in almost every case. Dead franchises can come back, just like dormant ones.
In terms of Nintendo IPs, some dormant examples
F-Zero: 99 just narrowly saved the IP from its dead status. The fact that it was dormant and then dead for a while means if we don't hear more in a few years, it will probably be dead again.
Kid Icarus: Dead status is rapidly approaching.
Star Fox: If it's not dormant, it's close to it. No new game for 8 years now (excluding the official release of Star Fox 2 over 20 years after completion), and nothing announced.
Donkey Kong: This probably counts. No new game since 2014, no new release since 2018, and the recent Mario crossover is a remake of the original Mario vs Donkey Kong. This is a really weird choice for Nintendo because there have been a lot of Donkey Kong games (platformers, spin-offs, etc.) but DK has gotten sidelined since the 3DS and Wii U.
BioShock is a non-Nintendo franchise that sticks out as dormant.

I think no entry in two console generations is enough to consider a franchise dormant. No entry in four console generations means its dead.

In addition, if a franchise has been dead I need a fully fledged iteration of the game (sequel, reboot, etc) to consider the franchise active. Otherwise it just goes from dead to dormant. F Zero 99 for example pulled FZero back into dormant territory, but it's still not an active IP just yet.

If there hasn't been anything in development for any given IP in 10 years

A console generation with no activity for said IP is pretty deserving of the dormant status.

Doesn't mean it's dead, with how dev time has expanded the last few years, some publishers don't have the effective to rotate all their available IPs effectively.

2 generations however ? Yeah, it's probably dead until it get some sort of reboot

I'd say a franchise is dormant if it's either

A) Gone 10 years without a new entry in development AND/OR

B) Is no longer available on currently supported hardware

Of course, there's lots of room for argument left to be had. For example, Mega Man isn't dormant because Mega Man 11 came out 5ish years ago on platforms that are still supported. But is Mega Man X dormant? It's only a portion of the franchise after all. Does the new content in the X Legacy Collection count as a new game?

To me, 15 years or more without a new game/remake released. Some examples:

Punch-Out!! (15 years)
Jak and Daxter (15 years)
Wario Land (16 years)
Final Fantasy Tactics (17 years)
Earthbound/Mother (18 years)
TimeSplitters (19 years)

2 full generations.

I excuse 1 generation because circumstances can impact the business validity of a new iteration. Especially now that game development times now can last damn near a generation to begin with.

Resistance, Ridge Racer and Bioshock are getting there, for example.

I've seen some franchises lie dormant for years and then get surprise releases. Valkyria Chronicles comes to mind here. I'd consider it dormant now since Sega has shown no signs of doing anything with the IP since 2018.

Like others have said, game development time only gets longer with each new generation, so calling an IP dead after missing one seems premature now.

So yeah, if there are no announcements, releases or ports within about two generations, then an IP is probably belly up at that point.