More details have emerged now with regards to "MIT no longer owns 188.8.131.52/8". Turns out, it's a big move from IPv4 to IPv6 on the MIT network, where the sale of their IP addresses are being used to fund the move to IPv6.
Fourteen million of these IPv4 addresses have not been used, and we have concluded that at least eight million are excess and can be sold without impacting our current or future needs, up to the point when IPv6 becomes universal and address scarcity is no longer an issue. The Institute holds a block of 20 times 10^30 (20 nonillion) IPv6 addresses.
As part of our upgrade to IPv6, we will be consolidating our in-use IPv4 address space to facilitate the sale of MIT’s excess IPv4 capacity. Net proceeds from the sale will cover our network upgrade costs, and the remainder will provide a source of endowed funding for the Institute to use in furthering its academic and research mission.
Source: Next Generation MITnet