It will almost certainly need one of those to adapt the rest of the manga at a sane pace, but that doesn't necessarily mean it will happen. Let's face it, anime not having an ending is Standard Operating Procedure, and it wouldn't be the first time everything except the final arc of a manga gets adapted (eg. Rurouni Kenshin).Think it's almost a given that there's going to be a part 2 / movie / few OVAs.
Which would mean a season break where there could be some manga spoilers doing the rounds