I think it would be best to create a character flag like PF_OLDASH or something to at least let older characters still use it.
I'd love to see a sonic AND tails redesign (more sonic though, since I think tails is fine) since Sonic's look this way for quite some time now!
The only thing a 64-bit build would do for this game is cause headaches when trying to play netgames. Nothing about SRB2 would benefit from running a 64-bit build as opposed to a 32-bit build, which runs natively on most processors and has an imperceptible, if any, performance penalty on the few that don't. So no.it will have 64-bit version? .-.
That thing is ancient and possibly even outdated compared to our current standards. I really wouldn't bet on its completion.