There isn't the capacity on LOROL trains to absorb the extra peak traffic from West Croydon to Epsom Downs I suspect. There may not be the line capacity to up the number of trains running that way either.
Most Southern Metro routes are already at least 4tph so I suspect if they were to be absorbed by LOROL the routes and trains would largely remain as now but painted orange - and as Physics34 says the biggest changes would be behind the scenes - ie you would no longer have drivers or trains that would operate a mixture of metro and coastal/rural routes.
Though ironically Beckenham Junction and Epsom Downs would probably get a Sunday service at last with the latter getting 2tph all day instead of just in the peak.
The dreaded mess room rumour mill is probably at work with the overheard drivers; it generates far more fantasy services and developments than any forum could manage!
It's SE metro that could really do with being taken over - as we've discussed before, there are plenty of unused paths in the evenings and on Sundays on SE network that could be used to give at least a 4tph service all week all day all routes.