I'd say the best option for IPs the publishers are not using would be to outsource them to smaller developers, while still holding the publishing rights to them, because let's face it, no publisher is going to willingly just give up any of their intellectual properties for free.

This way those unused IPs would not only remain relevant and in use, but it would also give the publishers an incentive to make use of them, as they could minimize their costs for them while also making profit by publishing them.

I mean it'd be cool if some dead IP's that are worth bringing back wound up in the hands of some passionate dev team looking to do just that, but the "Should" part of your title throws me off. If it had been "Would it be nice?" I'd say sure, but it makes very little sense to give up any IP's so they really shouldn't.

The main issue is that there's no real incentive to give up a dead IP as it may one day be in some way valuable, but by virtue of being dead they generally can't expect much compensation for it should they be open to selling it. That varies by IP, of course, but it's true more often than not.

I would like for publishers to give up IPs if they no longer intend on using them, yes. If you think deep down a certain property is no longer viable for your company, auction it. Don't just sit on it until it loses value. Sometimes corporations do use IPs as bargaining chips though.

No.

Fifty years or the life of the creator, which ever is longer. That is how long I think IP ownership should last before becoming public domain.  Either buy an IP or make your own if that is too long.

I think that IP laws are way too long, if more franchises/games were in the public domain it'd be great seeing all of the things that could be done with them.

Not really, since copyright holders right now like Nintendo would have to create new franchises in order to own the IP rights since their old franchises would be in the public domain.

Yeah, but if they want to avoid having others making use of the new game to promote their own titles they'd have to make a new IP.

Yes, because we have shitty publishers like EA sitting on their asses while holding C&C, Theme Hospital, Dungeon Keeper, Dead Space and many more IP's within their tomb.

I'm pretty sure there is a law that covers squatting on patents, there should most definitely be one for sitting on a game ip for years and years.

If that's the only to prevent its spread to the rest of the body.

No, like it or not it's their property to with as they please. Besides it is (as it should be) impossible to make anyone part with anything. I hardly ever use my car, but nobody can ever take that away without me saying so.