Based on what? I think we're in for both players but I don't think they're done deals personally..
Grealish it's constantly mentioned by people like Sherwood (a former coach of his) who has a good relationship that 'united are in for him, and he'll be a perfect signing', he asked Giggs the question too, but Sherwood is also basically saying he knows that Grealish to United will happen, 'terms agreed with the player' is the story.
Sancho again it's the same story, 'terms agreed' and haggling over the fee, but there are sources again that he wants the move and that he is the top target in the summer. Sancho is also travelling to the UK frequently from Germany to see his family, Dortmund know Sancho wants to be back in England. City don't want him, not whilst Pep is there (which Pep will stay 2 more years), Dortmund are also aware that he wants to leave (hence them benching him now). United also know they need to pay upwards of 80M and add-ons.
Sancho is also good friends with Rashford off the field which is another reason, and since he's played in Manchester with the City youth academy, Manchester honestly is a city he knows already, there are no other clubs really in England currently that he would just fit into (that are also willing to go for the player).
At the point given what several top tier journalists, and stories from people that come from parties close to Grealish and Sancho it seems like both deals are done honestly.
There are question marks over fees, players being sold like Lingard, Pereira, Jones, Smalling, Sanchez, and if United finish top 4 for the CL money, (for instance City getting to the QF of the CL netted them 80M in revenue, which would literally pay for a Sancho), so of course getting to the CL, and top 4 would mean that the budget can be widened a little.
Seeing a lot of transfer sagas honestly I'm pretty confident of Grealish and Sancho at this point. I think both will be United players... I would honestly be very surprised if those don't happen.
I do think United need a CB before Grealish but it seems both deals are done so I don't know what the plans are for a CB honestly.