There's not even an introductory post to the poll from a representative of Stardock or Ironclad? The players have to notice it themselves? That takes lack of communication to new depths... And 'an expansion'? What, just something new in general? That's not very informative!
I'm going to assume that the question should be 'would you prefer a new expansion to the existing game or a new game based on the existing interface?' which seems to make more sense. I'm a fan of the game's interface, its very solid. However the gameplay mechanics are to me somewhat lacking, what we have is a very unrefined game that has accreted rather than been developed. Some of the elements are just wrong, I'll attempt to explain briefly.
The fog of war element in Sins is both somewhat unique and rather bizarre. You can see everything in a gravwell except mines and Vasari scouts- but your space empire cannot detect gas giants in the same systemas your home planet. To know a gas giant is there you have to send a scout... Also, the explore element is somewhat curtailed when in order to find what a planet is like you need to conquer it first. You cannot decide to specialise in scouting in the game. Its just wrong!
The colonisation element of the game is also weird. Every planet, even the unfriendly non-terran ones, is precolonised by humans- who even the TEC faction is unaware of.. these humans might rebel in favour of neutrality if influenced by an enemy. You need your own colony to make these humans work, once you have a ground colony you then have a constructor ship.. in space. What? The colonies have a 'militia' and you have to destroy its siege ships, which will otherwise bomb you off the planet. A principal expansion tactic is to run in, colonise, start building turrets in space and then destroy the siege ships as they manoeuvre to avoid these turrets as they are being completed. Then you can move on.
All the planets are about the same size and have 2-4 'moons'. There are occasional special elements which often have to be unlocked, and then one or two only. There are mechanics that depend on the number of phase lanes leaving a planet.. this enhances mining, is bad for trade and has peculiar effects on propaganda. A more usual set-up would be that mining would be indifferent (because mining is short ranged by nature) and that multiple available lanes would enhance trade and propaganda. An extremely peculiar element is the limit on the number of orbital structures that can be placed around a planet. There are far better alternatives. Resources are infinite... a very basic decision on gameplay which has a great deal of effect, and leads to supply rules to offset it, which then begin to doom an empire trying to rebuild after a defeat.
The combat system has never led to balance in any version of the game so far. The counter system is weird and arbitrary and the weapon upgrades are either somewhat useless or devastating. Ship speeds are not upgraded and ranges only rarely. Empires can build huge vast complicated ships at first which then gain experience, but only very basic other types of ship which cannot become veterans. Why do cruisers have to be researched after battleships? Combat tactics are somewhat lacking. There are no ground troops! Space navies should have two essential functions: to protect invasions and to protect trade. Neither are relevant to Sins. The implementation of strikecraft is miserable. The relations system with the AI is a dungheap.
If you leave Sins and all its problems behind and reuse the same interface, with different basic design decisions, you could make a superb game, with many factions and an inherent tendency to balance. The interface is pretty, unlike the gameplay. Imagine a Sins setup where you had a single unified tech tree for all the factions. Lets have nine unique ship models per faction- escort, cruiser, battleship and slow, medium and fast. Then we can design ships.... more modules would be available with less speed. Every ship can gain experience. Each faction inhabits their planets and colonies, none of the cumbersome Sins backstory with all its problems. Enemy planets have to be invaded, or they can be glassed. Trade ships are vital to the games economy, not the equivalent of doodads. No more odd little mining entities around planets, if they are moons, then make them moons. The game design could be so much easier, so much more intuitive, so much more .. fun. So, no from me. Not even Sins 2. The interface is excellent, the story element- meh.