Basically, you're asking whether we should replace Thomas or Bradley with Hayward (basically signing Hayward will make it extremely unlikely you could sign both, so in effect that's what his signing will mean).
Right now, I would say Bradley, but that is based on some assumptions:
1) Thomas' injury will mean he won't reach the peak form he did this season ever again, though he'll still be very good.
2) A precondition to Hayward signing isn't that we have to re-sign Isaiah.
3) Thomas will demand a larger salary than Bradley, anywhere from an additional 6-10 million/year.
4) Fultz's defense will not be a strong suit right away meaning Bradley's D would be sorely required.
There's another little factor that I haven't seen mentioned: Isaiah is 1 year, 9 months, 19 days older than Bradley. When you consider how effective they will be during the course of their next contracts, you have to estimate Bradley at an extra 1.8 years of "peak" levels compared to Thomas. In fact, it's reasonable to assume that Bradley will still be near-peak throughout most of a 4 or 5 year deal (age 28-32/33 seasons).
Thomas will be 29.75 when the 2018 season starts. At the end of a 4 or 5 year deal he'd already be over 34-35 years old. Since his game is based on athleticism and he's extremely height-challenged there's a high chance his game would suffer more with age than other PGs. If he cannot get his shot off and his defense is a negative as usual, he'll essentially be useless on the court.
So yeah, put me in the Bradley camp if we sign Hayward. I am starting to think that Thomas won't get crazy offers in free agency though, for the reasons that I just mentioned and also due to the depth of the PG position around the league.