For me personally, I don't see a need for the new scale. I don't blow through modelling projects fast enough to be priced out of the 1/35 market. If I want a change of pace and wish to build something out of the box for cheap, Dragon is putting out some pretty decent stuff in 1/72.
As far as the pricing considerations, I don't always understand where Tamiya is coming from anyway. Their M4A3 Sherman circa 1981, is a decent kit that retails for just under 20 bucks. Their newer M4 (Early Production) uses a lot of the same sprues as the earlier M4A3, but retails for about twice taht of the earlier kit. It's a good kit and I don't regret having purchased it, but considering all the common parts with the earlier and far cheaper M4A3, I wonder if there it's retail price is artificially high? If Tamiya feels that it won't be able to sell its 1/35 kits because their price is so much higher than Dragon, I wonder why they would expect to do brisk business in 1/48 which I'm guessing would only be somewhat cheaper than Dragon's 1/35. I figure that a majority of serious builders would kick in a bit more money to build Dragon 1/35 rather than Tamiya 1/48.
However, the one bright spot here could be with younger modellers. I know when I was a kid, I couldn't afford good kits such as those from Tamiya and was forced to build mostly Revell, a lot of which were pretty second rate. If they're inexpensive enough, they might provide a good source of decent kits for todays kids, giving them something inexpensive enough to afford, while also being big and detailed enough to allow them to develop their skills.