Astra 2F is due to reach its 15 years of operational life in 2027/8, Astra 2E in 2028/9 and Astra 2G in 2030 - however the modern SES fleets have more often than not been able to get a few years more out of their operational lifespans (closer to 18-20 years before hitting inclined orbits that make them unsuitable for DTH viewing) and even then, as
@Analoguesat mentions, MEV vehicles could be put into place to give one of these birds service for UK spot beam services a few more years beyond that, if necessary.
There's been no announcement from SES as to any new satellites replacing the current fleet at 28E - they've essentially given up their 31.5E slot, taking the Astra 5B bird from there and moved it to 23.5E, renamed it Astra 3C and is operating a few transponders in tandem with Astra 3B. There's also been no announcement about replacing Astra 4A at 4.8E, which is now over 16 years old - SES5 (which is 4.5 years younger) exists there and could perhaps use its Nordic beam for broadcasting the Home 3 services in Estonia, Latvia & Lithuania, but it has no known pan-European beam IIRC which would mean not only the Ukranian services moving elsewhere, but also the SIS racing feeds aimed at UK & Irish bookmakers too.