Wittgenstein famously ended his Tractatus with exactly the same sentiment:
Woven man nicht sphrechen kann, daruber muss man schweigen.
(Whereof one cannot speak, thereof one must be silent)
That a famous philosopher, coming from a very different time, with a very different philosophical project comes to a similar conclusion one can say that this silence has to be taken seriously. One can say that his silence is at least authentic - rather than a 'cop-out'.
At the limits of thought, that is at the limits of what can be expressed there is only paradox. This conclusion is one chased by Graham Priest who developed a theory of true contradictions - dialethism.
Coming back to the Buddha, one of the questions he was asked is:
Is the world eternal?
...or not?
...or both?
...or neither?
This follows the logic of Catuskoti ; which elaborates the truth-conditions in Indian nyaya philosophy (true/false/both/neither) - or perhaps the origin of it.
After six centuries of debate, it was Nagarjuna who fixed 'answers' to these questions in terms of Sunyata (nothingness/fullness) and Pratiyasamutpada (dependent arising or becoming). They are noticably the first two terms in Hegels logic: Nothing & Being which are identified; and synthesised into Becoming; which points to a possible (and not neccessarily direct) influence.
Nagarjunas work, like Hegels work is cryptic, and unlike his compact.
So are the unanswered questions, actually answered?
To the extent that Nagarjuna does - yes (and one is possibly forced to add no, and both, and neither).