Supergirl CW Crossover Chances?

CV Article- Supergirl Not Crossing Over with CW Shows for Now

The showrunner of FlArrow (and now Supergirl), Greg Berlanti, said that CBS had no plans on crossing over but that he wants to do it and planned on building a bridge to do so. But after I watched the recently leaked pilot, I have my doubts they could. Kara has been on Earth for 11 years and her cousin (Clark a.k.a Superman for all you noobs), Clark has been a hero for a while when he found her ,he's 24/25, and since 11 years have passed he's in his mid 30's. So he's existed for at the very least 12 years and FlArrow has made no mentions of them. To top it off, Kara states that Earth has 2 heroes at the end. no mention of anyone else. It's gonna take a miracle to pull off a crossover or an multiverse crossover. What do you guys think?