It's expected that before a new Elise is unveiled, Lotus will introduce a different sports car, priced higher than the Elise. Exactly what this will be is a little uncertain, but will probably be either an Esprit-like supercar, or a midrange 2+2. The chances of them developing a new Elise concurently with this is pretty slim, given the status of that company and history of model rollouts to date. Thus, they'll most likely apply for an extension to the current waiver on the Elise. Will they get it? Hard to say. The first waiver was based on, I believe, financial hardship - they cited the cost they would incur to make it fully US legal, and compared that to income and current sales. Fair enough. However, will they be able to get an extension of that waiver if their sales of that model have been fantastic and they've been developing a totally different model in the meantime? It doesn't make sense. If they have the money to develop a new model, they could have spent that money on making the Elise US-legal instead (or so some might say).
So, picture this scenario: their request for an extension is denied, the Elise is no longer for sale in the US, and instead Lotus introduces a mid-range car and is still a one-model company in the US. Yes, any company would like to have more than one product for sale in any market. However, it's a pretty well accepted rumor/fact that Lotus is not making much, if any, money on every US Elise. All it's doing is helping to maintain and build their image. Why continue selling it if they can instead sell a PROFITABLE model here? So, I don't expect the current generation of Elise to be sold in the US very long at all - just long enough to build the brand and cover them until a new model is introduced. There may then end up being a one or two year gap before the next generation Elise makes it here.
This is all my speculation and guess, I have no inside contacts at Lotus (alas).