A number of stories have appeared, based on information leaked from among others CJ, that states that the new RV740 is not the successor of RV730, but more like a shrink of the RV770LE core used with Radeon HD 4830. This core sports 640 shader processors, 32TMUs and 16 ROPs. The memory interface is limited to 128-bit though, but thanks to GDDR5 the bandwidth should remain sufficient.
The 128-bit design and 40nm process all in all should enable a low-cost design and the suggested price tag of around $100 looks quite feasible right now as launching a fast mid-range card would fit in to the limited budgets most people have right now. Theoretic performance should be in the Radeon HD 4850 area, while we can't be entirely certain what the actual performance will be like.