People have been working on solid state for quite along time now, I think the current problem is to do with the speed, iam sure they (they who ever they is) will solve this.
Its a long term project, i would think we may see the early solid stat drives in about 5-10 years, though its soon think how fast technology has developed, dont we double the amount of transister per square somthing every 6months?
Although like you say - some thing better may come along