I'm not so sure that Mazda should worry about the Solstice. The Miata gave a new birth to sports cars when it was introduced 15 years ago. The MG for the 90's only reliable was what journalists were saying. The Miata has grown in size and power since it's humble beginings, never a beast in terms of power, it's excellent handling and relatively low weight have made it a favorite in autocross since it first came to these shores. It was such a sucess that the germans copied it with the BMW Z3 and now Z4 and the Porsche Boxter were direct responses to the Miata. Now the competition all have more power than the MX5, but they all have higher price tags as well. Along comes GM in a surprise move with the Pontiac Soltice/Saturn Sky, on paper a real fierce competitor for Mazda.
Now it's fair to say that I'm biased against GM, but the Solstice (and to a lesser degree the Sky) is a good looking car. and on paper sounds impressive. But GM has had a history of promising models that went nowhere. Remember the Fiero? The Reata? The Alante? Some very promising models that GM rushed to production and made improvements on, just in time to cancel them. I've heard that the Solstice is selling out even before it arrives on dealer lots.
That's fine, but GM will screw it up for sure and Mazda will be there with a much improved MX5 to scoop up those buyers.