When I go to that page I only see:
iTunes 12.3.3 for Windows 7 or later
After a number of years Apple (and other companies) probably decides there are so few users of particular system versions it is not economical to invest in development of software for those systems, particularly since some systems simply do not have the hardware or software capability to support new features. That's just the way it is with technology. I guess the overlying rationale is if you can afford a gadget you can afford the newer computer and the high-speed Internet connection too.
No, I would not anticipate Apple bringing out a XP/Vista version of iTunes.