The Wall Street Journal says that Musk has an incentive to go talk to Trump because, "Musk's various businesses are more dependent on the US government for revenue than most tech companies," notably from NASA for Musk's SpaceX work and federal incentives for zero-emission cars. Recode says that it is because he will be busy with SpaceX and Tesla work that Musk will not travel to New York to visit with Trump.
As for what the tech leaders who do attend will tell Trump, there will be some fawning. The CEO of Oracle, Safra Catz, emailed Reuters that, "I plan to tell the president-elect that we are with him and are here to help in any way we can. If he can reform the tax code, reduce regulation, and negotiate better trade deals, the US technology community will be stronger and more competitive than ever."