The biggest constraint on 5G Wi-Fi is that the signal attenuates too quickly after passing through the wall.
Like many technological advancements, 802.11ac is very complex. This must be a very bad thing, especially for a technology in the general consumer market. Vendors and industry associations like the Wi-Fi Alliance have done a lot to hide the complexity from end users. So there is hope here. However, 802.11ac increases the number of settings and choices between transmitting and receiving devices. Therefore, it is difficult to set user expectations about the functionality of each device.
We just described power as one of the good things. However, power remains a challenge in 802.11ac, especially for devices that are high-bandwidth data sources. To achieve the highest available bandwidth in 802.11ac requires the use of up to 8 RD transport devices. In contrast, 802.11n allows up to 4 transport streams, however, there are very few devices capable of 4 transport streams, mainly due to power and other RF challenges. Full implementation of 802.11ac capabilities may take a long time.
The number of transmission devices and the power supplies that drive them are not the only implementation challenges. Beamforming, a feature that 802.11n does not yet provide, is also part of 802.11ac. This is just one example of this complex technique. This technique needs to be implemented to achieve maximum data rates, because this technique is documented, it does not mean that this technique is easy to implement.