I understand that licenses are tied to a single device unless you use a licensing server. For the size of my environment, a licensing server is rather overkill and was not recommended. As there is no way to migrate the concurrent user licenses to new hardware, and with user licenses being the most expensive part of a MAG purchase,concerns have been raised about longevity of investment.
The SA series hardware looks to have had 5 year lifecycle from announcement until end-of-sale. If the same is going to appyl for the MAG, which came out in mid-2011, there is only about 2 1/2 possibly before end-of-sale. I won't have any issues with using end-of-sale equipment in product as long as it has support, and I know support runs for 5 years after end of sale, BUT, there are concerns about what the software development will be done on end-of-sale hardware. Do I run the risk of finding myself with an OS release (MS is moving towards yearly releases) that isn't supported on my 2 1/2 year old MAG investment? I don't know.
Thus, with no way to move the bulk of the investment (concurrent user licensing) forward to new generation hardware, the lifecycle of the hardware relative to our purchase date is fairly important.
When I look at a major competitor like Cisco ASA, their 1st generation ASA's were on the market 8 years before they went end-of-sale. Will the current generation last that long? Not sure, but all I can go on here is history. If the MAG hardware is going to run 8 years, then now I have 5+ years of known currency, which is very differnet than 2.5 years.
How do others address these kinds of questions and situations?
The best venue for these types of discussion is your Juniper partner or sales team.
In my experience, when issues like you describe occur they can generally find discount incentives for the migration of the licensing cross hardware platforms. They also have the forward looking outlook on where the product line is headed so they can help select the right hardware platform out of the gate.
With the SSL vpn series, the MAG versus SA has not played out as a feature support issue. Essentially the same SA software is running on top of two different hardware integrations. I don't expect that SA hardware will have any feature issues with the constant churn of windows versions.