Selected Answer
I haven't used much PowerPoint. Therefore my answer is theoretical, as befits your question, and it is an unequivocal "Yes". The link can be provided by VBA.
VBA is available to all MS Office applications and, conversely, all Office applications are available to VBA. Therefore a VB macro running in PP can access an Excel workbook and extract data from it and, conversely, a VB macro running in an Excel workbook can access a PP project and make changes to the text in one of its slides.
From a practical point of view, you would first have to decide the flow of both work and logic. Is it that you want the PP slide to be updated when you open the workbook? Or when that particular cell is modified? Or is that you want the slide to be updated with whatever is in the Excel cell at the moment when you open the PP project?
Depending upon the answer to this question you would either have to write a procedure in VBA for Excel or for PP.