Recently a new Pokemon series was announced; is it a response to this? Is Ash finally being retired? A good way to send him off.
I don't think it counts as a 'reponse'. The Alola series was reaching the end anyway, and the new series always launches alongside the new games, so it was just a reflection of the timing.
I can see it being feasible that this is Ash's last series. Having won a league tournament, the show could say tjis means he can now be classed as a Pokemon Master, which was his original goal, so it would be a natural end to his story. That said, he also won the Orange League and beat all the Frontier Brains, which could have also given him the same status and the show continued.
The new show said it will featured as prior regions so bit unclear what the plan is. 29th September is the full reveal so guess that's where it'll become clear.