Is there likely other significant objects we haven’t discovered in the solar system? In the last few weeks, I read a few news that presented new advances in our understanding of the solar system, which implied we don’t really know our neighboorhood that well. I was wondering, how likely is it that we make a significant discovery around us in the next decade? Like discovering a new massive object (moon or even planet etc.), or that a planet area is habitable 

I was assuming it’s very unlikely because we have good measures and models (gravity based or other means I guess) but those few papers (sorry I didn’t bookmark them) have me wonder. How much do we really know of our nearest environment, before looking at interstellar stuff?
Moons.  We've explored the planets up to Saturn with probes that remained in orbit for long periods and found moons down to quite small sizes.  While it is certain that there are more small undiscovered moons, these won't be large spherical objects.  Uranus and Neptune have not been visited by orbiting probes, and so there are surely lots of undiscovered moons. Nothing very large, or we could see it from Earth but relatively substantial moons could be orbiting Neptune but be undetected. However there are no planned missions to either Uranus or Neptune in the next 10 years.

Dwarf Planets.  There are probably spherical bodies (and hence "dwarf planets") in the Kuiper belt, in the region of space around Pluto. There could well be further discoveries of dwarf planets here. We are certain there are no more dwarf planets in the asteroid belt. On the other hand we discover new asteroids all the time.

Major Planets.  There is the intriguing suggestion that the orbits of the known Kuiper belt objects are correlated with each other in a way that could be due to a large, Neptune sized planet in orbit in the outer part of the solar system. It is far from certain if such a body exists, but if it does, it could be discovered within a decade.

Habitable zones.  The only Habitable zone is the one which is approximately 150,000,000 km from the sun.  If you go closer, water boils. If you go further it freezes. Liquid water surely exists under the ice of some of the outer solar system moons, but I would not call them "habitable".

Unknown Unknowns.  If you look back 10 years most of the new discoveries could not have been predicted.