I would treat any rumour of Universal putting their name to this project with a pinch of salt. It may be that London Resort Company Holdings have spoken to NBC and Universal about potentially using some of their IPs, however I very much doubt it would be a full universal park, especially given the current deals with BBC and Aardman. Even if it did turn out to be a Universal park, it would be unlikely we'd see Harry Potter included given the existing Studio Tours attraction already in the UK - I strongly suspect there would be some form of measure preventing a competing attraction being built and therefore taking the Studio Tour's customers away.
The most likely scenario we may see is that one or two Universal film IPs used as the basis of attractions or shows which would sit alongside other IP based attractions e.g. those based on IPs from the BBC, perhaps in a Motiongate type set up where different areas are based on different companies/studios. As for the current plans, until they are submitted to the government then they can be easily adapted and modified. However, due to the development having the Nationally Significant Infrastructure Project status, the plans which are submitted need to be extremely detailed and there will not be the scope to change and amend them once approved (unlike with plans submitted to local councils where developers can apply for amendments after approval). This means that when the plans go in we should know what range of rides we will be seeing, even if they don't yet have IPs for them all.
I read that on the way back from The Warner Bros Studios...
But that is a good point made, on one hand you have an obviously successful IP you could use but
it would make the london studios vistor number drastially drop, a way they could use it though is if they were to use the Fantastic Beasts brand instead but that would stop any FB developments at the Warner Bros Studios which, and after seeing the FB sets for next years film today(I'll make a seperate post about that soon), I would be a shame to not see the FB sets.
However if the Universal rumoured are to be believed, The Decipicable Me brand and the upcoming Nintendo Land would probably come to the park.
I personally think however, that we could see a Motiongate Style park as Motiongate has a Dreamworks area, And with Dreamworks being owned by NBC Universal, just that LER could be looking into Dreamworks brands.