This would not be a graceful transition because you would need to first remove all of the supporting components from the first ARC or BEAM (one by one), then add them to the other ARC or BEAM (one by one).

Is there any other way to have a smooth transition between both tv’s?

Because I am not sure how would I be able to create two surround setups for two tv’s on the same room without the need to buy another sub and another 4 speakers.

Using any type of equipment, proper surround sound requires that the TV is placed between the L-C-R speakers used with that TV and the surround speakers are typically placed behind the viewer.

If the TV’s are on opposing walls it would be possible to swap the front and rear speakers when watching one or the other TV’s, but this is not practical with SONOS.

One approach using a standard A/V receiver would be to use a receiver and a giant speaker transfer switch to swap front and rear speakers when using one or the other TV. There will be other issues, such as attempting to use Apps on one or the other TV. This will not be straight forward because receivers and TV’s only have one ARC input.

I think that the least expensive approach would be to use two A/V receivers, one for each TV, and a speaker selector switch to exchange front and rears between receivers. Subwoofer placement is more relaxed and, while not quite optimal, a subwoofer could be shared between systems (with minimal trickery).

Do you really need two surround systems? If you only need two screens, some A/V receivers support connecting two screens.