Such a decision would ultimately rest with the Kingdom Seneschal based on the results of a formal membership poll - but one group being able to opt out when the rest are keen to go ahead is not likely to be an option.
The main factors requiring an all-or-none move relate to the need for contiguous geography, viable numbers, regional coherency and national jurisdiction.
Depending on the poll results, such a scenario might be addressed by attempting to tackle/mitigate any major concerns raised; postponing or delaying any move for further discussions; or going ahead if the consequences of abandoning a transition are seen as too severe when the idea is well-supported everywhere else.
Where do we go from here?
The first informal survey in 2020 indicated sufficient interest to consider further work on the concept. This led to more discussion, formation of working groups, feedback and iterations with the aim of developing a widely-consulted, acceptable Principality bid. The 2023 informal survey confirmed ongoing support and thus is likely to lead to future discussion and development work and possibly further informal surveys.
If or when that process comes to fruition, we can then request a formal poll administered by the Kingdom Seneschal to gauge overall support for an active move to Principality status.
For more details on the discussion and formation process, see Bartholomew's Roadmap.