I'm in the humanities in NYC, and I think I know the institution you're talking about. (I have friends who teach in similar places, at the very least.) Usually a lecturership in a school like that is a term-limited thing. You might get a one-year contract, or a two-year contract, maybe you'll even get lucky and get the opportunity to renew that contract a second time. But it will be made very clear in the contract you sign that the contract is not open-ended. That means that if they're going to have to pay more money for you in year 5, in terms of benefits, or negotiated salary increases, then your contract will not be renewed for year 5.
If an open-ended position does come open, the dean, or the chair of the department, or both, will want to conduct a national search to hire someone for one of those open-ended, tenure-like positions. The fact that you have taught at that school, and have relationships with those faculty will mean absolutely zero in that search. You'll be competing against several hundred faculty, most of whom will have not only PhDs but an increasing number will even have prestigious publications.
There's not really a way to sneak into academia through the back door, especially in a geographically desirable location like NYC. You might be able to go somewhere rural and find a community college type job without a PhD, but even those are increasingly competitive.