If it has not been successful by now, you really need to look at doing other things.
Also you should not be basing your offering on what the current hype is, but rather on filling a need and offering something people want and will use. When the hype fades, atleast then you will (hopefully) have something of value that will last beyond it.
The world changes so rapidly and most of what small startups offer are solutions to a current need. If you are doing it as a hobby or for fun/learning/charity then that is different, but as a business (the purpose of a business is to make money, and startups are businesses ultimately) it is unfeasible. As a basic proof, try pitching to investors/VCs. Even friends/family would be reluctant to invest as a business.
Even without knowing the details and complexity of solution, I dare say unless the value is in core algorithm/architecture design that can be migrated, much of what they have done will be outdated (based on assumption the technology-stack/tools/learning/knowledge they use is now getting outdated).
Time to market is not always as crucial as it seems; photo.net was doing photo sharing and social networking ten years before flickr got bought by Yahoo!, it's more than possible to be too early to market.
You don't go to VC's during the R&D phase, you go to them once you've worked out the technology risk and have something that could be taken to market with a sufficient application of money.
It's a good thing that there are inventors with long attention spans because we would still be chasing wildlife for dinner if there weren't.
If you are reluctant due to the time/effort already invested ("letting go" is a common problem), then perhaps what the others are suggesting is actually in your best interest(s) and doing you a favour.
anyway lets resolve the internal issue first. You need to find out what your partners really want, chances are they want/need something else than what it looks like from outside, find out what will motivate them to stay with your project?, also it is not clear whether they prefer to quit or they prefer to change the concept, may be they want to quit because you're not flexible enough to listen to them and change the concept - you need to really listen to them and think rationally (not emotionally) whether changing the concept will benefit all, try to create a win-win situation for all. last option is to let them go (because if they are not motivated enough then it won't produce the desired result) without burning the relationship, find the replacement at the earliest. If they are united and want to close the company then find out the legal way to hold on to the intellectual property at the minimum cost to you....
if they are your true friends then they should not give you hard-time in exploring either options. If you really love your project then you have to be very firm though in a polite way so that they can figure it out that you're really serious to pursue your ambition and nothing can change your route (with or without their help) - may be they will change their mind after seeing your determination.
1. Determination: as pg always says that most successful people are those who're determined to bring their dream come true.
2. Code: somehow you have to manage to get the source code in your control. ,
3. Backup plan: make plan-b ready for damage control anticipated by your partners leaving project.
4. Speed: buddy, you need speed to roll-out to deal with competition.
EDIT: somehow you have to make an agreement with your partners (if possible do it legally) that if they decide to quit or if your partnership is dissolved then IP (code) remains with you (because originally the idea was yours) and in the future they cant do something similar either, i dont know whether it is completely enforceable legally but i dont think if any company (say goolge or yahoo or MS) will let me pursue the idea on my own that was originally not mine - so in the same way you can have an agreement or contract with your partners too.