If we return the Malvinas it will be the same thing as decolonization. Taking a piece of land and colonizing it is know as colonization. So, giving the land back and no longer having access to it would technically be decolonizing it. Of course there are a lot of factors that go into decolonization but overall this would be consistent with decolonization.
First of all, it is technically true that the Falkland Islands are a British colony. However, in this usage it should avoid the traditional negative connotations associated with the phrase "colony". At the time of British Colonization there was no Indigenous American group which lived on the island. The land was not, as far as anybody knows, used by mainland Indigenous Americans for anything.
Thus, it was perfectly acceptable for a European power to colonize the Falklands. Argentina has no valid claim to the island and its 1982 Invasion of the Falklands was a blatant violation of international law. It would be an injustice to nobody for the UK to maintain its rule over the Falkland Islands indefinitely.
The UN Decolonisation Committee and the British Overseas Territories had an issue with each other. Basically it was felt by many that they needed to establish a more modern relationship. The territory of the Falkland Islands (Malvinas) being returned would I assume mean it was being decolonized. The people of the Falkland Islands were British and voted that they wanted to remain that way. The UK had sovereignty over the Falkland Islands. I wasn't aware that constitutional link was severed. Until it is then it won't be considered decolonized.