If the new 7.5" Surface, reputed to sell for $400.00, runs Windows RT, it's obviously DOA, since total worldwide sales of ALL RT devices in 1Q2013 was only 200,000 from ALL vendors.
If the 7.5" Surface runs Windows 8, then it will be underpowered for that price, and most likely the true cost for a functioning unit will be $500.00 with necessary "upgrades". It's very unlikely there will be a compelling reason for very many people to want to buy such a device at this price point.
Even worse, massive advertising won't help Microsoft sell either of these things, because their previous ridiculous Surface ads and the subsequent failure of the Surfaces being advertised are still fresh in the minds of anyone who was paying attention.
The most interesting part of this will be whether Microsoft DOES in fact offer an RT version, because if they DON'T, then that signals they've given up on RT.