You're not helpless, neither is your child. First, "at risk" for autism can be like "at risk" for diabetes. If you can nail down his diagnosis so much the better. Therapy works miracles in developmentally at risk children. Miracles.
Work the problem. Get your kid the help he needs and monitor his progress. Be an active part of his treatment plan. You aren't helpless.
I can wholeheartedly second this. The diagnosis for my nephew when he was not talking or communicating as a child was that he was likely to stay that way, and that my brother and sister-in-law would be essentially babying him his whole life.
A couple of weeks ago, he took a day off from his job to fly down on his own to see a Diamondbacks game with my parents. He's a huge Yankees fan, but he spent part of the night commiserating with my mom about Paul Goldschmidt being traded - he felt that the Diamondbacks could still succeed, but that they'd miss his production.
You. Just. Never. Know.
And believe me, there will
always be people to help you. The people I've met who are committed to working with autistic children and teens are some of the best I've ever met. If your kid turns out to be autistic, it will be a challenge, but you don't have to go through it alone.