Stealing (or being influenced by or whatever you want to call it) the design wouldn't lead to misdirected traffic. Not owning the .com is what will do that job for them.
http://www.icann.org/en/dndr/udrp/policy.htm
if they can prove registration in bad faith and that the owner has no legitimate interest.
If the twitvid.com guys really did buy the domain and design the site after twitvid.io got started, maybe they could somehow prove that stealing their thunder was the only "legitimate interest" and that the domain was acquired in bad faith.
Sadly it sounds like an uphill battle -- and even in the best case it might be a Pyrrhic victory as trademarks take the better part of a year to issue (if not more) and the UDRP procedure probably isn't speedy either. And then they'll fight it, and you'll spend all your time in court instead of building your company.