Huh? This is what you are calling a roadmap? https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2015-December/011865.html
Blockstream/Core made it clear that they didn't want Bitcoin to scale, thereby forcing people onto the Lightning Network. Since the Lightning Network doesn't really exist yet (and there are many unanswered questions about its security and viability), the markets responded by moving volume over to altcoins. Bitcoin dominance has been cliff-diving in 2017, today it's 56%: http://coinmarketcap.com/charts/#btc-percentage
Bitcoin has a lot of inertia due to name recognition, services, and hype, but eventually it will slow down as it becomes less useful. With the mempool reaching new all-time highs as we speak, we should be seeing a lot of unhappy bitcoin users in the next week. Some of them will flee to alts, and others will leave the space entirely.