LangChain is still around but that doesn't mean much. MCP isn't much better.
MCP solves a data and API integration problem.
Both are concrete things that people need to do today. AI agents talking to one another is not a concrete problem that organizations building features that integrate AI have today.
I didn't feel the need to use Langchain, chaining LLM calls is usually just a few lines of code (I think even fewer than when using Langchain).
For example, most companies have an internal directory and internal private APIs and tools. They can build an agent to help complete internal tasks. However, they also may purchase an "HR Agent" or "Travel Assistant Agent" or "Tax Preparation Agent" or "Facilities Control Agent". These agents aren't sharing their private APIs and data with each other.
It's also difficult to model these agents as structured tools. For example, a "Tax Preparation Agent" may need to evaluate many different options and ask for specific different documents and information based on an individual users needs. Modeling this as 100s of tools isn't practical. That's where we see A2A helping. Talk to an agent as an agent.
This lets a user talk to only their company agent and then have that agent work with the HR Agent or Travel Booking Agent to complete complex tasks.
MCP is solving specific problems people have in practice today. LLMs need access to data that they weren't trained on, but that's really hard because there's a millions different ways you could RAG something. So MCP defines a standard by which LLMs can call APIs through clients. (and more).
A2A solves a marketing problem that Google is chasing with technology partners.
I think I can safely say which one will still be around in 6 months, and it's not the one whose contributors all work for the same company.