As a newbie to SL and a mesh content creator I do not know how to digest all of this. If it is true that Linden Lab will continue to let Second Life operate as is, then that leaves little to worry about. I do not have to be concerned about the hundreds of dollars I have spent on content and I can continue to see sales of my products for this platform. I would imagine that It is not in the best interest of LL to shut down SL in favor of a new grid otherwise it would upset a lot of people and cause a lot of harm to their business.
Linden labs has every right to create a new closed sourced platform/world. That does NOT mean consumers MUST adopt it. Closed source DOES NOT MEAN more security, otherwise we would not have to worry about trojans in Microsoft Windows right? Closed source does not stop hackers from stealing content. It only prevents third parties from bringing new viewer features to the table and it prevents innovators from improving the software or forking it. At present there isn't a 64bit official SL viewer for my favorite OS (Linux) yet Firestorm offers a feature rich viewer in 64bit which runs very well on my distribution. That said, I would not even be using Second Life if it were not for third party viewers. There needs to be a way to keep the community in the loop.
At the end of the day I think the new platform will be a hard sell on existing linden residents. My computer I am using is not even capable of running SL at the highest possible quality without stuttering a little and that is one thing which is attractive; people do not have to upgrade their hardware to enjoy these virtual worlds. My computer is not a race winner, but I know a lot of people who use SL with systems that are a lot older than mine...
LL will need a way to convince people to abandon their present SL investments to move onto the new platform. I do not have a clue as to how they will achieve this but I am willing to bet they might need to offer more than keeping your screen name, friends list and linden dollar accounts. Several grids claim they can offer "more" yet when we look at them it is far from the truth. Providers such as Kitely, Inworlz or OSGrid cannot succeed because they do not have an audience and as such the content developers will not make products for those grids because the consumer base is not there!