Sounds like Rigby plan to pour money into BOH in order to increase terminal capacity in expectation for 2mppa. Once Bournemouth can prove itself it quite possibly will be the defacto gateway airport for the south coast.
The challenge for SOU is the business market hasn't been the same since Brexit and COVID-19, and the reduced operational hours and load restrictions make it a tougher decision.
SOU may have better road and rail connections vs BOH, but SOU's proximity to London i.e. not being convenient enough to be a 'London' airport and being too near and with too many constraints reduces its chance of being a busy regional e.g. BRS, LBA, puts it in a grey area.
I've said this before, but in the absence of one 'true' south coast airport, I think the best reality is for BOH and SOU to complement each other like Belfast's Aldergrove and City.
However, if the money gets spent on infrastructure at BOH, I can't see any reason why Easyjet wouldn't take a look at some routes that aren't currently offered by a LCC on the south coast.