If I had to guess, XP will be maintained (unofficially) longer and better than 98 was. It has a lot bigger user base. Although it's different than Win 7, 8, 10, etc, it's not as different as the 9X systems. 98 supplied the proof that an OS can be maintained past Microsofts so-called "end of life" and be made better than anything they ever did for it. 98 was used to establish the methods and create the tools, tools I expect should see a lot more development on XP. 9X and its users proved that "end of support" is not end of life.
I will migrate to XP if I'm forced to, but I'll need better hardware to get the same amount of work out of it. I tried using XP to run the Tor relay on this PC. It rarely lasted a full day. With the same hardware running Lite98SE with the modifications I've found here, it would last 2 weeks or better before needing a reboot. AFAIC, XP can be made reasonably secure with a lot of stripping and service disabling, but it's always felt like I had to fight the OS to get what I wanted from it, or more accurately, to get rid of everything that I don't want. With 98, it did what I wanted and only what I wanted, then stayed out of the way. I wish MS would get off of this twisted "computing experience" concept of theirs. Ones computing experience shouldn't be influenced by the OS. People don't use operating systems. They use programs that run on that operating system. Microsoft don't seem to know the difference between an interface and an obstacle.