You could also add a TC
Yes, but if you really
need the extra reach, you should just invest in a longer lens. Teleconverters often degrade the optical quality and slow down the autofocus, I'm not really a big fan of them. If you do end up needing one in the future, stay away from any other brand besides the brand that makes the lens (ex. If you buy a Sigma lens, buy a Sigma teleconverter, if you buy a Nikon lens, buy a Nikon teleconverter, if you buy a Tamron lens, buy a Tamron teleconverter, etc.).
Teleconverters generally come in 3 different magnifications, 1.4x magnification, 1.7x and 2.0x. I'd stick to the 1.4x if you have to use a teleconverter, as it doesn't degrade the lens' quality too much, keeps the AF speed reasonably fast and costs the least.