Q: Future support for current mac pro?

They will not stop support when the new model is released.

2008 3,1 is still supported.

Lion supports even the 7 yr old 1,1

OS X support usually spans about 5 years. Hardware support continues until a device is declared as obsolete. There's no definitive term for that, but about 7 years is in the ballpark. Mac Pro 1,1 is still supported.

Actually Apple has very definite deadlines for when they drop hardware support for a product. They declare a product "vintage" when a product has been discontinued for five years but less than seven years, and "obsolete" when a product has been discontinued for seven years. Hardware support for "vintage" products continues in the State of California, USA, but is terminated everywhere else. Hardware support is completely terminated for all products designated as "obsolete".

http://support.apple.com/kb/HT1752

Regards.