It will continue to be available, but I'm not sure what the performance increase is. There'll be a blog post on walkingrandomly.com coming in a few days - a guy who benchmarked it when it first came out. See http://www.walkingrandomly.com/?p=5220

Real-world max for single-thread speedup is probably the 3x quoted for the cache-busting SunSpider benchmark, with around 1.5x being more common. In terms of issue width, the new core is only a modest improvement as the Cortex-A7 is largely single-issue.