Cleveland in particular didn't gamble on Andrew Bynum and spend six million on Jarrett Jack to back up Kyrie because they're still in rebuild mode. Cleveland is going all-in on playoffs now, as they should, and Rudy fills the gaping hole in their starting lineup at small forward since Bennett is apparently targeted to play power forward primarily. Rudy arguably turns Cleveland from competing for a 7-8 seed into a credible 5-6 seed contender.
I think Charlotte is still hedging their bets on going all in, but if they have an early good run like they did at the start of last year when they went 6-4, there's a good chance they take the plunge. They have a much rougher start this year (their first ten games include Houston, Miami, and two with the Knicks) but if they go 5-5 over it, say, I think there's a good shot they go for it.
Dallas, like LA, would probably need a tertiary trade partner to make work, someone who likely takes Vince.