In an announcement made on the Bitcoin development mailing list, Bitcoin core developer and Bitcoin Foundation chief scientist Gavin Andresen suggested that, if the development community could reach no consensus on increasing the one-megabyte block size limit, he would shift his efforts from the main Bitcoin implementation (Bitcoin core) to the alternative Bitcoin-Xt implementation.

Such a move could represent a watershed moment for Bitcoin as a whole, as it would mean that its former lead developer would effectively leave his own project to join a forked version.

Bitcoin-Xt is a patch placed on top of Bitcoin core and developed by Mike Hearn, developer of Lighthouse and Bitcoinj. While Hearn is a vocal proponent for an increase in the block size limit, Andresen's contribution to the mailing list does not specify what the new maximum block size on Bitcoin-Xt would be.

He does indicate that he will not settle for 20-megabyte blocks, as he proposed for Bitcoin core. Instead, Andresen will likely push for an additional automatic increase of the limit, possibly by 40% per year, as he has also previously proposed for Bitcoin core. He wrote:

“If we can't come to an agreement soon, then I'll ask for help reviewing/submitting patches to Mike's Bitcoin-Xt project that implement a big increase now that grows over time so we may never have to go through all this rancor and debate again.”

In order to ensure Bitcoin-Xt will gain traction and eventually overtake Bitcoin core, Andresen announced he would lobby influential entities within the Bitcoin ecosystem to adopt Bitcoin-Xt and bigger blocks. These entities would include mining pools, exchanges, payment providers and wallet services. If successful, Andresen would presumably force opponents of the increase to join the network with bigger blocks — or end up isolated on an “old” version of Bitcoin. As Andresen put it:

“The purpose of that process is to prove to any doubters that they'd better start supporting bigger blocks or they'll be left behind, and to give them a chance to upgrade before that happens.”

Raising the block-size limit has been a controversial issue for several years. Satoshi Nakamoto originally intended it to be a temporary measure in 2011 to prevent spam. Several developers and other prominent Bitcoiners now believe a limit on the block size may actually be required in order to safeguard the decentralized nature of Bitcoin and provide a long-term incentive for miners to secure the network. While it seems that most developers currently agree that the block size at its current limit of one megabyte is too small, consensus over how exactly to move forward is still lacking.