It is very likely that yes, although it is possible that they will release one related to AI or new robotic troops perhaps? Although I think that in lower ages there would be more missing (ages)
Whether it's the last age or not, the extra levels per upgrade likely means it'll be a long while before they have to think about another age.
Or they could just take the easy way out and add another 10 lvls in a year or 2.
Why would this be last one? It would make sense if they made 2025 as final age. But if they went step ahead and designed future age, then its only the BEGINNING. Now we will have command and conquer style stuff, mammoth tenks, laser weaps, etc.
Many thought Information Age was the final Age, but the Ages kept on coming. So while it's normal to speculate and assume this all must end, because everything in life does end eventually, it's impossible to say.