Is new System becoming Legacy System too Fast?

We do have days of discussions spread across months. Then we come up with so called "Next Generation" design. Boast around developing a futuristic system which going to solve all our problems. Customer going to get huge ROI and so on.... Does it really happen? Or is it otherwise?
I happen to have discussion and explorations with one customer in late 2005 and after multiple discussions and  trend analysis and their design and implementation phase customer goes "Live" with new system in mid 2009. And here comes January 2011 and seems same futuristic system is a Legacy System including its data. Now customer is considering another new system which address their problems spread across multiple countries and have a consolidated system. It is 'Good for Consulting' but as being part of product development forced me to think don't we have optimal and faster ways?
How to shorten our "long development Cycles" and provide customers real futuristic systems before it is  another legacy system? This is forcing me to think and explore and find new ways to speed up these implementations. Allow customers to use benefits of system before it becomes legacy. It saves their energy and investment can be used to do more with same data. Only way forward is come up with few tools which can speed up this process.

Everyone says Agile methodology works well. Not sure How will it help our customers in the long run if is followed during product usage? How and what are possibilities will think and share soon.

-Ritesh

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