Per notes from a public Internet Relay Chat (IRC) meeting, the code for Taproot could be ready for users to active in the Bitcoin Core client via “Speedy Trial” in May of this year. If Speedy Trial is successful, this would mean the upgrade could be online in November.
“There is broad agreement that we should target something like a May 1st release, with [a 1 week signalling start time afterwards],” Bitcoin Core contributor Jeremy Rubin wrote in meeting notes. If successful, this would mean an “activation time of around Nov 15th,” he notes.
Speedy Trial allots a three-month trial period to see if miners representing at least 90% of Bitcoin’s hashrate will signal their support for the upgrade. If this threshold is reached, then Speedy Trial is successful and the upgrade will be "locked in." After this, Taproot’s rules would be officially enforced in another three months.
(If, for example, signaling were to begin on May 7 and miners showed sufficient support, then Taproot would be locked in on Aug. 7 and go live on Nov. 15. The later the signaling begins, the later the activation.) New code in Bitcoin Improvement Proposal 8 (BIP8) will set the parameters for the Taproot activation, which will judge when to lock in the upgrade based on block height.
As stakeholders appear to be in agreement on the timeline, bitcoiners finally have a (more or less) concrete deadline for when they can expect Taproot’s code to be available to the public to download, marking an end to what has become a painstaking road to a relatively simple upgrade.
Taproot activation’s and the long road to consensus
There is still the caveat that May 7 may not be the exact start date of Taproot’s activation, but it will likely be somewhere around that time.
As ever in Bitcoin’s development, upgrade parameters are in constant flux because no single person or organization has final say over how development should proceed. It’s up to Bitcoin’s distributed, international community to come to a consensus on what changes to make to Bitcoin and, just as important as evidenced by the Taproot activation discussion, how those changes will be brought online.
Take the so-called user-activated soft fork (UASF) that was so hotly debated during the Taproot activation discussions. This would give node operators the option to force-activate Taproot should miners fail to update their own nodes with the upgrade by rejecting blocks from noncompliant miners.
Miners have given no indication, though, that they will reject Taproot, and the UASF proposal lacked enough support to make its way into Bitcoin Core, the software implementation that 99% of the Bitcoin network runs.
Still, Luke Dashjr and others are coding a UASF that anyone can opt into (but which won't be included into Bitcoin Core) in case Speedy Trial fails. If Speedy Trial were to fail, then nothing would happen and Taproot would simply fail to activate. Under this scenario, a UASF could be deployed, probably next year, to bring the upgrade online.
Thanks to Ben Carman for feedback and input.