From 3rd January, the Xelabus website states that the X4 will be split, with the Eastleigh to Velmore section becoming a circular X4A Eastleigh - Velmore - Eastleigh. The timetables have not yet been formally published, but
looking at BusTimes the X4A looks set to run hourly 0945-1445 with a 1545 terminating at Velmore. Under the current X4 departures from Eastleigh to/from Velmore are 0830, hourly 0940-1640, then 1800. The X21 Science Park service will also be reduced to three trips each way down to two (0645 and 0815 from Southampton returning 1630 and 1800 - currently 0700/0800/0900 returning 1610/1710/1810.
Source:
https://xelabus.info/updates/1031
The Hants Bus Update blog also says that they are cancelling their former Yellow Buses Bournemouth tenders 18, 33 and 36 from 15th February. No official announcement appears to have been publicly made that I can see, but the blog can be found at:
https://hantsbus.blog/2022/12/changes-at-xelagroup (unable to copy and paste for quote).