That is absolutely not a problem. If a player said yea Lebron told me he wants to play together and I said he should come to Miami, and he said cool. Then Dwayne tells Pat Riley...there is no problem. No official of the team ever spoke to Lebron in this scenario.
And as for "planning" for it. It could never be proven...because I am willing to bet Pat Riley as well as all the other teams that did would have been planning for free agency of 2010 anyway. So, it doesn't hold water in my opinion.
It's tampering. If there were any evidence that the Three decided in 2008 that they would team up in Miami this offseason, and Wade went back and told Pat Riley to make it happen, the NBA would do something about it. It doesn't matter if he would have been getting ready for free agency anyways.
I doubt that it could be proven. And it's a little far-fetched, mainly because Miami offered contracts to free agents the past two summers, including Lamar Odom last year, so they didn't quite play it like they were just waiting for 2010.