Some sort of Trump/Cruz alliance seems to be forming according to this article:
http://www.washingtonpost.com/blogs/post-politics/wp/2015/07/14/ted-cruz-and-donald-trump-to-meet-wednesday-in-new-york/Now I agree with Chaim that Trump really only cares about... Trump and that he loves attention. I do not think his addition to the race is a negative though. I feel he will bring up important issues that other candidates will not bring up and will move the conversation toward the right instead of toward the left where Bush and others want to drag it. Trump is going to wake a lot of voters up, and may be the spark that ignites the dormant conservative base in this country.
Trump loves to think that he is an outside of the box deal maker and I assume he wants to make some sort of political deal with Cruz. Sadly this probably involves him offering Cruz some sort of political payoff (Job in a future administration, VP slot, etc...) to drop out of the race and support him. I assume Trump's ego is too large for him to step to the side and become part of team Cruz, you never know though.
This theoretical deal may also be Trump developing a long term political strategy where he knows that Cruz and him have no shot at the Republican nomination, but if they team up behind the scenes now they can form alliance that will allow them to form a serious 3rd party challenge with Trump at the top of the ticket and Cruz as the VP. I could see Trump even allowing Cruz to be VP, but in fact be a defacto-Co-president with almost as much powers as a President, just as long as Trump has the presidential title (and thus top billing) I think he is satisfied.
Trump probably recognizes that Cruz is the smartest candidate out there and he wants to somehow makes sure those smarts are not used against him and instead are used to help him.
This could get very interesting.