The changes to direct trains are permanent for the time being. There should however be a connecting service at Norwood Junction to East Croydon which doesn’t appear to operate at the moment - presumably as a result of the short term timetable changes. Once this is back and running, there should be a connecting service every half hour, e.g. 7:25 departing Forest Hill, arriving at Norwood Junction 7:36, and then 6 minutes later leaving there arriving at East Croydon at 7:46.
A similar option already exists going the other way, although with a worst case 15 minute time to wait at Norwood Junction, as the Overground train just leaves at the same time that the Thameslink train arrives there.