YES Is the short answer here.
Of course, the reality is a bit more complicated... @Marek has already outlined the major areas where you may have conflicts between your two solutions, but to recap:
- DLLs (make sure you don't produce two DLLs of the same name from both solution, make sure you reference the same DLL versions in each solution)
- Solution files such as cshtml, config, aspx, ascx, js, css
- Serialized items. If you are using TDS or Unicorn to serialize/deploy content items, then beware of overwriting the same item from two different places especially common folder items e.g.
Note that config files could have conflicts both in file name and path (an obvious issue) but more subtle problems too, such as one config file removing an element and another adding a child beneath it etc.
Provided you are disciplined and consistent in your approach this should work. You could place most of your files into solution-specific subfolders to help organisation. e.g.
One final thought (which I appreciate is not answering your question!); since you are using SXA, you are probably using Helix architecture in your solutions? Might it be worth merging these two solutions together making the distinction between the solutions as separate "Project" layer projects? If you have different teams working on each site, you could potentially manage that by working on different branches within the same repository. You would then make your deployment process easier too!