Microsoft has released Windows 10 Technical Preview for phones, but only for a very small number of low-end devices (Lumia 630, 638, 635, 730, 636, 830), so most of us are out of luck. The reason for this limited initial release is technical in nature.
Some context on why we chose these and not higher end phones like the 930/Icon or 1520: We have a feature that will be coming soon called â€œpartition stitchingâ€ which will allow us to adjust the OS partition dynamically to create room for the install process to be able to update the OS in-place. Until this comes in, we needed devices which were configured by mobile operators with sufficiently sized OS partitions to allow the in-place upgrade, and many of the bigger phones have very tight OS partitions.
I only have an HTC 8X, which technically should get Windows 10 eventually, but since it’s not a Microsoft device I doubt it’s very high on the priority list.