As other have said, try them out. Use other softwares and see how comfortable you are with them and if they fill your needs.
After that you can have a better opinion of each one of them and see if you need them or not.
Now my opinion hehe
Rendering: Cycles certainly isn’t the best render engine on the market, but it is really good being a free render engine; so in that department you have a great treat for free. I’m saying this because all the big guns in the industry right now can be really expensive if you add them to the price of Maya, Max, C4D or even Modo. So, maybe you don’t want to have Cycles as your main render engine, but it could be helpfull to know it so it can save some money sometimes. It has helped me a LOT with small archviz projects.
Modeling: it has it’s quirks, but modeling in Blender is really good (also taking into account it is free). But for a more complete solution I would go to Modo. Plus, the BGE could be of use to test your textures and shaders before exporting to a game engine.
VFX: …a tricky one. Since VFX almost always includes simulations, you’ll have to find another software, like Houdini or thinking particles. Blender can be used for some basic things, but if you want to put a giant lizard destroying NewYork you’ll have a hard time doing it ALL in Blender (not impossible of course, but it would take some more time to do).
For motion tracking Blender is a really good alternative to Syntheyes or PF Track, so I’ll keep it around for this task.
Composition… There’s a free version of Nuke now, and Fusion has been launched for free too. So I’d go for one of those. Even Natron is shaping up pretty good.
Anyway is a good thing to know other softwares