Yes - desktop Excel VBA remains essentially unchanged from the 2007 version and should run all your old code without a problem. If you get 64 bit Office there may be some issues with calls to dlls, but that is fairly easily fixed.
Microsoft seem determined to switch everybody to JavaScript, but the last time I looked at it (a year or two ago) the whole process was very cumbersome and complicated, and there were also some basic issues with JavaScript and big numbers, which may or may not be fixed.
Another alternative is coding in Python and linking to Excel with pyxll (commercial) or xlwings (free open source). This works well (once you get used to several Python eccentricities), but it does require learning a whole new language, and even after getting reasonably familiar with Python the coding process is nowhere near as quick and easy as using VBA. The de-bugging process in particular is much easier and quicker with VBA. The main advantage of Python (from my point of view) is access to useful libraries for just about anything, including much better curve-fitting, solvers, and linear-algebra routines than are available in VBA.
For running code in the on-line version of Excel, pyxll (but not xlwings) completely bypasses VBA, and calls the Python code directly, so in principle it should be possible to set that up on-line, but I haven't tried it.
Finally Microsoft said (several years ago) that they were looking at incorporating Python into Excel, but that seems to have gone quiet.
Doug Jenkins
Interactive Design Services