The debate over Rondo's relative trade value now vs. later or at the trade deadline is fair because no one knows. Rondo may play great, may get injured, may get frustrated with losing, may be about what he was last year. What can't be debated is that the clock is ticking so to speak and a trade now gets you Rondo for the whole season but a trade at the deadline gets you Rondo for a couple of months. All things equal, I think most teams would rather have Rondo for the whole season. That is why I think waiting would more likely backfire than pay off.
In terms of probability that he resigns with us, that is also a fair debate. Right now, Rondo could sign for 3 more years on top of this year for a contract that would result in 4 years/$57M (that is assuming the maximum allowable extension has been offered by the Celtics). Since that deal has not been made, it is fair to assume Rondo is looking for more years or more money. I actually don't think it is about money. I think Rondo wants control and the ability to choose where he plays and who he plays with. I don't think he will decide based on money.
It appears that the Celtics are going to be a bad, young, mis-matched team. Why would Rondo want to resign here if max money/years is not his primary concern? If Rondo was committed to the Celtics either out of loyalty or "accept the challenge" mentality, he would take the extension. The franchise simply cannot afford the risk to roll the dice and let Rondo play out his contract and then walk.
Call it a rock and a hard place or what ever you want but I hope the team faces the reality and does what they need to do. Rondo is a good player and you can hold out hope that he will resign without us over paying, that we then are able to pull off another couple of miracle trades of picks and parts for all stars, then attract a couple of fill in the blank FA, and presto, we are right back in the hunt. Swing and miss on that though and we set the franchise back years.