I don't know the numbers, but I'm assuming that like Rondo, if Love were to sign an extension this summer, the number he could command would be less than if he gets to free agency this summer.
Does anyone have the details on this?
There are no official numbers, because max contracts are based off the same revenue numbers as the salary cap, and will be finalized in July 2015. However, based on the recent revenue projections put forward by the NBA in April, Rondo and Love would each be eligible for a max deal with $19 million as the year 1 salary, and 7.5% raises each year, for a 5-year total of $109 million. If Love were to be traded in July, and sign an extension as part of that trade, he would be paid $16.7 million in 2015-2016 (which is just the option year of his current deal), and $18 million in 2016-2017 (compared to the $20.4 million he would get from year 2 of his free agent deal.) He would then become a free agent, because his extension could not last beyond 2016-2017. All told, Love would have left about $5 million on the table in the first two years, and would probably find himself at a lower salary in 2017-2018 than he otherwise would.
Rondo's max free agent numbers are the same, but his extension numbers are different. If he signs an extension next year, he would make $13.9 million in 2015-2016, about $5 million less than his max. His extension could only run through the 2017-2018 season, compared to 2019-2020, and would be worth an average of a little under $15 million per year, compared with the $20.5 million per year over the first three years of a max deal. While I'm open to debate whether or not Rondo should be a "max" player, I 'm comfortable with him being worth more than 75% of that amount. I would be completely shocked if Rondo signed an extension, as would Danny.
(Also, inevitably people bring up LeBron when talking about max deals. This requires two points. Firstly, LeBron's max is a few million per year higher than Love or Rondo's. So they're not the same. Secondly, LeBron would easily command $30 million if there were no max salaries and only a salary cap. Everyone knows this. You can't compare player X's salary to LeBron's, because LeBron isn't making what teams would be willing to pay him. It's said that rookie deals are good because they help save salary room. Another good thing is having a superstar who's salary is capped, because he's essentially subsidizing the rest of your team.)