X64 is an extension of the x86 instruction set which is copyrighted by Intel. In other words it's a derivative that Intel has control over through their copyright on the x86 instruction set. The value of x64 is entirely dependent on the x86 copyright that Intel holds so it's worthless to anyone else without a license for x86 from Intel. I have no doubt that the contract that allows AMD to use the x86 instruction set copyright includes clauses that will protect Intel and their use of the derivative x64 in the event AMD breaches the agreement by being acquired.
I like AMD but the fact is they can't be purchased because if they are their primary product is lost. You people are living in a fantasy world if you think they could be. The contract that allows AMD to use the x86 copyright is explicit that those rights are lost when the company is acquired. Hell the only other real consumer x86 license is held by VIA which had acquired Centuar and Intel sued them claiming they breached the no purchase agreement. The only reason they weren't terminated is that VIA held a couple key patents that Intel needed so they gave them a 10 year contract extension. But now that Intel is focused on power use VIA's entire market segment has been lost and they haven't developed a new processor since 2011.
There is a chance Intel will loan AMD money to keep them limping along so they avoid anti-trust review but I doubt it highly these days. Intel has a legitimate argument these days that ARM and other processors now provide adequate competition even though Intel still mostly controls the PC segment they are non-existent in the portable tablet/phone category which ships far more CPU's. In fact ARM has begun to harm Intel's margins which is a key sign of competition. The wintel monopoly was crushed by Linux.
If AMD runs out of money and can't get an influx of cash they will likely see much of their business lost and simply go out of business.