Although it isn't definite we will see you tomorrow, it is quite ____________.

The term "likely" is the correct choice for this sentence because it serves as an adjective that conveys the probability or expectation of an event occurring. In this context, it modifies the situation of seeing someone tomorrow, indicating that there is a good chance it may happen, even though it isn't guaranteed.

The other options do not fit the grammatical structure of the sentence or the meaning required. "Likelihood," for instance, is a noun and would require a different sentence structure to be used correctly. "Unlike" is also an adjective but conveys a sense of dissimilarity, which does not match the intended message of probability in this context. Finally, "likeable," an adjective that describes the desirability of someone or something, does not apply to the situation being described. Therefore, "likely" is the correct and most fitting choice here.