It was expected that they would leave F1 since their performance was getting worse and they could not keep up with the development of other manufacturers. However, with Renault's exit from F1, it will also create instability for Alpine, because from the information circulating that many Alpine employees protested against it since they had been developing the engine expected for 2026. But Renault's own reasons are quite considered because they want to reduce the financial risk because of their involvement in F1. But whatever it is, Renault must have considered carefully about their departure from F1 and hopefully it will be the best choice for Alpine.
I also read about this and the confirmation that Renault will abandon F1 engine project came after much controversy over the idea of effectively ending its operations in this sector of motorsport.
Protests from the Viry's team, an alleged cost saving that would be obtained by Alpine following the customer route instead of financing its own engine program and in the end the clarity that the preferred path was indeed to acquire the engines from Mercedes in the long term.
In my opinion this is a wise decision, because in addition to the financial benefits, this agreement means that Alpine will have access to a more competitive engine, quite different from the current one that has little power compared to its rivals.
Finally, as far as I know, discussions with Mercedes are still ongoing and nothing has been formally announced yet regarding a future partnership, so it is not possible to "bet" on it. However, this is indeed the best alternative for Alpine.