Talk about bad timing... I purchased a Spectre x360 8th gen not long ago... though I'd love for it to have an HDR monitor with an Adobe RGB color space, that's so far been my only disappointment. But I also couldn't wait any longer; my Razer Blade Stealth wasn't doing the job (crashing a lot), and I had work to get done... sigh.
To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.
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I felt that way after buying my Spectre x360 at the end of 2016, right before they came out with the newer version that had pen support. I couldn't wait any longer either. Until someone starts leasing the latest hardware and letting you refresh it every few months, we'll always be stuck with that problem.
There is always going to be something even more awesome in 6 months time. If one would always wait for the next best thing coming up, one would never buy anything 
One way of how manufacturers are thinking about getting around is popularizing device as a service options, where you can upgrade/switch any time at a minimal cost, as opposed to making huge investments in hardware you may not need or need to change. We're still a long way from this being mainstream in consumer space (in the professional/workstation space it's far more popular), but it's an option.
2017 HP Spectre x360 15 i7-8550U GTX150 + GTX970@16Gbps-TB3 (HP Omen Accelerator) + Oculus Rift + Win10 [no guide]
HP Omen Accelerator Thunderbolt 3 enclosure legs stand removal walkthrough
Employed by HP, but my posts and opinions expressed on this forum are my own.