Cascabel’s tacos have been flying off the grill so fast that after nine months, owner David Chiong and his chef-partner Todd Mitgang are already moving to a larger space three doors down at 1538 Second Avenue (formerly Willy’s Bar and Grille). So what will happen to the old space? “We’re hoping to bring another fun spot to the Upper East Side within the year,” is the only thing Chiong will reveal. “We have a few ideas one of them being dim sum but for now, our focus is on tripling Cascabel’s reach.” Don’t be surprised if Chiong’s Cuban-Chinese roots have a significant role in the flavors of his future venture. (Dumplings, anyone?) Either way, both the new Cascabel and its currently unnamed replacement at 1542 Second Avenue are due to open later this month.