As I see it, you should be the best person to make that call. A salesman can tell you about all of the new bells and whistles on the latest product, but if you can't justify it on your own already, then there is no reason to upgrade.
My reccomendation is this: baseline your traffic for a month or so. See what is going on in your network. What does your company want to do in the future? How will this impact performance of your network? Do your homework. Justify the need to upgrade to something. Not necessarily 6500s. Cat 4000s may very well be enough for what you need to do. Go through the basic motions first. This will not only provide you with more thorough knowledge of your network, but will also allow you to make good business judgments on when and how to upgrade. I hope this helps.
I wanted to share this because I have in the past worked with someone who wanted to upgrade to the newest technology as soon as it came out. This put a lot of undue stress on staff and finances.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...