Formula E has a 25 year-long exclusive license for single seaters on electric. That doesn't rule out the possibility of a merger happening at some point in the future.
[https://www.racefans.net/2020/06/18/formula-1-formula-e-merg...]
[https://www.racefans.net/2020/06/18/formula-1-formula-e-merg...]
All F1 teams have signed the Concorde Agreement until 2025 - which means they're "committed" in one sense or another. I don't think FE will be in a position to attract Mercedes and Renault fully by 2025 (the two mass-market manufacturers who'll be most heavily influenced by the move to fully electric, with toes already in the waters in FE).
The late 2020s will be a lot of political posturing, and should FE look to be attracting F1 backmarkers with promises of cheaper overheads, more future-relevant tech and decent audiences in addition to manufacturers, 2030-2039 will be interesting as heck.