It is not only LAMP and .NET, but other technologies like Phyton and Ruby that are being widely used. But I don't see it as getting the market share of other frameworks but getting specialized in one aspect. LAMP is lightweight and fast but still not a great idea for transactional applications. Phyton is ideal for information retrieval applications and Ruby is very maintainable. .NET is not lightweight nor yet trusted for transactional applications and suffers from scalability but if scalability is not your concern, it is great because of the ease of development. And Java is still the best candidate for enterprise and transactional applications like financial applications.
It is interesting that in the early years of SE, the programming languages like Cobol and Fortran were very specialized for certain usages. The idea of general programming language gave birth to Pascal, C and later, JAVA. But now again they are becoming specialized but not at syntax level, but at the level of solution stacks and frameworks.