1. Yes, we will largely return to offices. Digital tools remain sub-par as replacements for direct human contact / communication, and that isn't likely to change soon. (Mayyyyyybe mixed reality will finally make a dent here, but meaningful computer-supported collaboration is still a very active area of academic research. Haven't found any tool that comes close to the fluency and reliability of a quick huddle around a whiteboard.) As others have noted, there's also a lot of investment in commercial space - so there will be economic / political pressure to return to office work.

Will this happen in 2021? No idea. Some workplaces have announced full-remote until mid-2021 at the very least, and any cure / vaccine will take time to fully study, productionize, and distribute. It might take a few years to fully return, and there may be a slightly higher proportion of WFH even after that.

For a historical perspective: consider that humanity has weathered catastrophic pandemics before, and look to what happened there in the longer term. This time around, we have the further advantage of much better medicine / logistics than, say, during the 1918 flu. (We also, of course, have both the advantages and disadvantages that come with much faster communications channels.)

2. Absolutely not! By working from home, I'm taking on additional office-related expenses that would normally be paid for, plus expenses related specifically to remote work (e.g. webcams). If anything, I'd expect the company to help cover those expenses, and/or bump my salary up to compensate for added setup and logistics on my end (or even just to reflect the reduced overhead on their end - if they save money having me work at home, why shouldn't I see some of that?)