No, he did not need to disclose them, since as you write, the assessement had not been made yet: it was, at the time of the sale, speculative, with no knowledge of exactly when (if at all; the projects could have been indefinitely delayed or fallen through) and how much an assessment would have been made. A seller is not required to disclose things of which he has no affirmative knowledge and which are possible but not certain. The disclosure requirements only require disclosure of what is known to the seller. Further, the assessment was not under his control and affects the whole building, not merely the interior of his unit, which is what, as a condo owner, he owned: a seller needs only disclose conditions which are in the property which he personally controls, and does not need to disclose larger "community" issues which affect multiple properties and which he does not contorl or affect.