Id personally save the hassle of hoping for firmwares that work properly with G.INP and future vectoring and avoid lantiq chipsets all together
The ECI openreach modems you refer to and homehub 5A devices are lantiq just like the TP-Link W9980, infact those 3 are the exact same chipset, that being the Lantiq VRX-268 chipset. The TP-Link managhes to support it via bitloading modification script in the newest firmware, the ECI and HH5A from Openreach though are basically (IMO) doomed to never support it at all.
NO Lantiq VRX-xxx chipset AFAIK has supported G.INP out of the box (by that i mean when devices were released). Some of them also do not support vectoring which is worth having as that will likely be deployed over the next couple of years. BCM63168 BCM63268 and BCM 6368 chipsets all support G.INP even on their earliest xDSL driver revisions, there has been NO device that uses those chipsets which has not supported it or needed firmware updates. Even the Homehub 5B (broadcom chipset) supports it out of the box, though thats a bug ridden mess itself (NOBODY buy one of them unless you want bug ridden junk which crashes )
I know they are the same but they are one of the ones that either a) will never support it like the modem or b) like the HH5 highly unlikely to support it, this has already been written about a thousand times already.
Regardless of your personal non expert opinion or how they have managed to get them to work the Lantiq chipset devices are mostly working and they still have the benefit of working better than the Broadcom devices on longer lines, this has been proven by people with the actual test equipment to prove it.
Does it mean I would still buy Lantiq over Broadcom, probably not as all my Broadcom devices have always performed better for me and every time I have strayed from Broadcom I have regretted it, however credit should be given where it is due, regardless of personal opinion.
I am not a fan of Draytek but I still have to acknowledge the simple fact that they have got there Lantiq based 2860 and 130 working with G.INP and Vectoring and they have got it working well and fast. Less issues than the ASUS devices
You where the one in other threads saying you would buy Draytek if you had the money and they use Lantiq, so do you a) Really not like Lantiq or b) Just not like the other manufacturers who have poorly implemented it.
Also if Netgear produce a D7000 with Broadcom and a D7800 with Lantiq, they must have some level of faith in Lantiq for a premium device.