The Cabinet will meet tomorrow to decide whether to overhaul the rent pressure zone system.
It's been suggested the 2% cap would be retained for existing tenancies, but wouldn't apply to new apartments after a date to be decided.
Government leaders are considering whether to link rent increases to the rate of inflation instead.
Threshold CEO John Mark McCafferty says it's vital ministers protect tenants.
"We'll see what happens in tomorrow's cabinet meeting. Clearly, despite its flaws rent pressure zones as they exist they have helped to moderate rent increases, and without it tenants would likely face substantial rent increases.
"The absence of rent pressure zones, or the absence of some sort of rent cap, could push more renters into financial distress, or maybe even homelessness."
