I mentioned this earlier but technically the first patient ever to fully recover from this type of brain tumor occurred early last year after a few years of experimental trial treatment and there are other very rare cases of long-term survivors even if the tumor is not fully gone. So there's a hypothetical path based at least a bit on reality if they decide for MC to try experimental treatment and/or get very lucky.
And even if they don't go the route of being fully cured, it could be left open-ended with the tumor not actively progressing and in the epilogue MC is just committed to making the most of the uncertain time left.
So I personally am not going to assume to know the ending for sure until we're seeing it, because it still could go multiple ways.