The phrase "to warrant a sequel" means that something is good enough or successful enough to justify creating a second part or continuation. Full definition
I thought anchorman was funny, but does it really warrant a sequel? (filmjunk.com)
Master of Monster for Genesis sold well enough to warrant a sequel on the Sega Saturn, but is still relatively hard to find. (blog.pricecharting.com)
These numbers are not an extraordinary success by the standards set by most Hollywood pictures, so why this film warranted a sequel is beyond me. (rottentomatoes.com)