Yes, I've read his book. But it predates this dark energy discovery (or surmise). Inflation is compatible with flatness, with homogeniety, smoothness, etc. All issues related to the early universe, I believe. Off hand, assuming this extra kicker to the Hubble constant is a development which occurs late in the history of the universe, I see no conflict. But I need to ponder this. If we can observe this accelerating expansion now, it's early days when it happens, isn't it? But it's after the inflationary stage, so I think Guth's work is safe. That's my preliminary take on it. (Clearly, I'm babbling, and I'm not the one to ask for an authoritative opinion.)