Hasn't happened for me and I am in a 5G area.
According to the t&c which seem really badly written you need to have a "5G sim plan", which wasn't an Oomph option but now is .
So where I have the ultimate oomph unlimited data, a new selection of extra fee capped data tiers exist between the bundle one and the upgrades... one of them is called 5G and is capped at 5gb or something like that.. The way the press release was written it suggests those on a "4G" plan as the legacy are called will stay on EE and therefore 4G until VM switch everyone to Vodafone at the end of the EE agreement. People new to VM who choose a "5G" plan will be put on Vodafone and as long as their phone is capable get 5G.
That suggests those already signed up to 18months on the fastest broadband and biggest tv package bundle who then selected their "ultimate" deal with unlimited data sim won't get 5G until 2022... i.e. their best customers they really wanted to upgrade to their most expensive bundle will be the last to get it!