It seems likely that inter-grid teleportation will become a commonly-available and trivially-usable feature within the next twelve months. While there are efforts underway to establish and implement underlying supporting protocols, it really doesn't much matter if those efforts go ahead or not. Functional inter-grid teleportation can be implemented solely in the Second Life viewer with or without the cooperation of the servers -- if not by Linden Lab, then by a third-party. That makes the lingering promise of a broad range of other relatively ubiquitous virtual environments seem tantalizingly within reach.
While Opensimulator currently offers hobby-level performance rather than the sort of heavy-duty production-level performance that many are looking for, the ability of Opensimulator to handle server-side tasks is still not to be lightly dismissed. Simple to set up and configure, and modest on hardware requirements, anyone capable of installing and configuring a simple network would be skilled and knowledgeable enough to install the software and set up a simulator or two or twelve. Even Microsoft is jumping on that bandwagon, working on integrating a number of features that don't necessarily advantage the platform.
Whether we're talking integrated grids, or micro-grids (groups of simulators running as a standalone group), Linden Lab believes that the basic limitations of transport to external grids (no connection to Second Life assets or inventory, and no connection to the Linden Dollar) will keep 99% or more users on the Second Life grid. It seems quite possible that somewhere among future business models, Linden Lab is planning to monetize interconnection fees, to bring third-party simulators within the main-grid fold under the Linden Dollar and the provenance of main grid asset and inventory servers.
However, for many users, communities and organizations the disconnection from that currency and those services is an attractive advantage, and we believe that the number of users and organizations who might partially or wholly migrate from the main Second Life grid may be much, much larger.