Will GW ever return to WFB?
If you mean drop Age of Sigmar and return to WFB, then no, I don't think there is any chance of that.
They will be doing Warhammer Legends, which will be a section on the Warhammer Community site for legacy warscrolls for the old armies, combined with a series of Made to Orders - which will start with Dark Elf miniatures - though nothing has been announced as to when this happening. Other than that, i don't think in the short term we will see support for the game Warhammer Fantasy Battle. However, products set in the old setting - well Warhammer Fantasy Roleplay 4th edition (made under license by Cubicle 7) is rumoured to be out in the first weekend of June, and we may find out more about that at Warhammer Fest in May.
Also, while this year's main Specialist Games release is expected to be Adeptus Titanicus, the original launch of the Specialist Games division did mention Mordheim, and I expect that when they do get around that, it will be set in Mordheim in the World that Was, rather than move it to another setting such as Shadespire.
Now ForgeWorld have done their own version of the 40k 7th ed rules just for Horus Heresy, there may be a possibility that something like a FW version of the 8th ed WFB rules might come along. I wouldn't hold my breath on that though. FW support for either WFB or AoS has never been much good. My personal opinion is that they've never really had fans of WFB who understand what FW could do for the system, nor for AoS, though I have heard they are setting up a dedicated AoS team within Forge World that should start putting out products this summer.