I suspect that any new version that currently doesn't work on XP, won't be modified to work. 3CX, like Microsoft wants everyone to "move along". It's understandable, seeing as, I'm sure, it takes more time and effort to make a product backwards compatible. Given that XP won't be having any updates after April 8th of next year, the feeling is probably that many users, especially business, will be "encouraged" to update before then.
In other words...I wouldn't hold my breath if I were you.