playing with and against that collection of talent is good for him. If he wasn't playing there he'd just be playing pickup games with lesser talent. I'd say it could only help him improve...
But I think at Rondo's age... he is what he is. I don't see him getting any better. His stats might go up when the big 3 retire and he takes a bigger role. But he's 24 now. He's like the same age as LeBron.
24 year old players don't get any better? 
Rondo will certainly improve. If he will improve his shooting remains to be seen.
Who knows, really... for every Steve Nash there is a Tracy McGrady who peaked at 23 and went down hill from there. LeBron hasn't changed much the last few years. Kobe's been the same player since age 22. Jason Kidd at 22 was about the same as Jason Kidd at 28/29 leading the Nets to back-to-back Finals.
Seems unrealistic to expect a major jump in his game. He's 24 years old. 24 isn't a kid.
Kobe has become much more skilled since he was 22. He used to be mostly a slasher but know he has diversified his game in a ton of ways and has become a much better jump shooter. He has worked to develop a whole post game and has a variety of unique pivot moves you don't see anyone else use. If you think Kobe has not gotten better since 22... Idk what to say. He may have started regressing due to miles and injuries but he got much better after he was 22.
LeBron has become back to back MVP for the last couple of years... so yes he has also gotten better. He used to be completely unable to shoot and was merely okay on defense but now he is a solid jump shooter and is the best defender at his position in the NBA.
Jason Kidd also used to be a much better defender. He has become a much, much better shooter late in his career as well.
Players who don't get better are usually an exception to the rule. I guarentee Rondo will get better, he has shown improvement every year in the league... why would he not continue to improve? I don't possibly understand your thinking.
Oh Sure... Kobe picked up a few tricks along the way, but at 22 he was a superstar averaging 28.5 points, 5.9 rebounds, 5 assists and 1.7 steals on 46% shooting... helping his team win a title... which is about even with the 27 points, 5.4 rebounds, 5 assists and 1.5 steals on 46% shooting that he averaged last year when he helped his team win a title.
You're right on LeBron. Back-to-Back MVPs at age 24 and 25... while his stats have stayed pretty much identical to what he did at age 23 (when he probably should have won the MVP as well)... Ok?
Disagree on Jason Kidd becoming a "much better shooter". His shooting % at age 23 is about what he averaged during his years on the Nets. Maybe you're talking about washed-up Jason Kidd who recently saw his shooting improve when he benefited from a different style.
I'm sure Rondo will get a bit better too. But I'm not counting on him having any major changes. He probably is what he is (more or less). Luckily, he's one of the best point guards in the league.
Apparently you just blindly use stats and don't watch the games.
Kobe has become a much better player and has also become one of the most clutch players in NBA history, which he was not back at 22. Those "tricks", as you call them, like a post game and jumpshots and all sorts of moves are actually extremely valuable to being a complete offensive player. And all that was after he stopped playing alongside Shaq, one of the best Centers of all time, who drew a ton of attention away from him and gave him the ability to be open much more often. He was not the man on those teams, Shaq was. And this year Kobe has regressed due to injuries, it was not his best year past 22. He has also become a much smarter player over the years.
For LeBron, playing defense doesn't come up on the stat sheet unless youre stealing or blocking shots, which he does (in the open court I don't remember a more impactful defender, something that he also has added in the last few years btw), but he also plays great individual, straight up on your man defense. Again, something you have to watch to see, can't just look up stats. LeBron wasn't making All-NBA defense before man. And even if his points totals haven't gone up overall his jump shooting is far better than it was. That's plain to see.
And Rondo is "what he is" as you say, obviously, but he will become a better and better version for the next few years until he hits his prime.