I'm sorry, but, no.
Blizzard is MOSTLY sticking to the games, and the most advanced firearms there were rifles used by the Dwarves. Not SubMachineguns like a Thompson or Mp5 or whatnot.
And tanks? They had the Seige weapons...though remember, those things SUCKED against infantry, and were only useful for buildings. (Which we don't really do in WoW)
Now, being able to make an Epic Mount that looked like a tank...that could be kind've interesting...but having something "modern" with machine guns, firing canon shells, treads, etc...just isn't going to work in a "Quasi-Medieval Fantasy Game."
Edit: In Alterac Valley, you do see some interesting gadgets on the Alliance half of the map. On top of Balinda's fort is a huge cannon, there's catapaults and seige tanks all over, what looks like a cannon on a tripod can be seen near Icewing Bunker as well. Although, none of this is operational, but it'd be interesting to see it in use.
Edited, Jun 25th 2006 at 2:56pm EDT by Kleptomaniac