Israel accepte UN Res. 181, but the Arabs rejected it. Res. 181 therefore no longer applies. The Arabs killed it. But you are correct that the 1967 lines are not borders, but armistice lines. Israel's final borders were to be determined by negotiation under UN Res. 242. (The REAL 242 the the UN actually voted on, not the altered version the Arabs rely on.) Unfortunately, we do not see the Arab side entering into honest negotiations, but only making demands they know cannot be accepted.
UN: Gaza could be 'uninhabitable' by 2020 if trends continue (AP)
from the article: Palestinian PM: Declaration of statehood just a formality