Abhinava Shankara in his commentary on Rudram says Vyuptakesha refers to Sri Adi Shankara Bhagavadpada. Sri Chandrashekarendra Saraswati Mahaswamigal says the same and quotes Abhinava Shankara's commentary as reference.
This is what Sri Chandrasekharendra Saraswati Mahaswamigal says in one of the talks:
In addition to being the several things of this world, there are also
the names of the form of parameshvara which we know. These are called
asAdharaNa nAmas. Usually, we understand sAdhAraNam as ordinary and
asAdharaNam as something special or rare. The fact is sAdhAraNam means
what is general and asAdhAraNam means what is specific. When
paramashiva is referred to as the several things of the world, such
reference will be in the plural form and the asAdhAraNa names which
are exclusive to paramashiva are mentioned in singular. While
mentioning names specific to shiva, it is said, bhava, rudra, sharva,
pashupati, nIlakaNTha, shitikaNTha; note that the names are all in
singular. After the name shitikaNTha, the two names kapardI and
vyuptakesha are mentioned with namaskAram immediately followed by
sahasrAkSha (one with countless eyes) and shatadhanvan (one with
countless weapons). Then the names girIsha and girisha are mentioned
which which are specific to shiva are also mentioned. Thus, due to the
occurrence in the midst of the several asAdhAraNa nAmas appropriate
only to parameshvara, the names kapardin and vyuptakesha are listed,
it means that these two are also specific to Him.
What is meant by kapardin and vyuptakesha? Kapardin means the one who
is having jaTA. Vyuptakesha means the one who is having a shaven head.
In rudra, names given to Ishvara in succession are opposites in
quality. He is jyeShTha and he is kaniShTha. In the same manner, he is
the one with jaTA and the one with the shaven head. But there is
something special about kapardi. Kaparda means jaTA. But it does not
refer to the jaTA of everyone. Only the jaTA of parameshvara is called
kaparda. When mahAviShNu, brahmA, indra, and all the other devas are
wearing a kirITa on their heads, it is only shiva, the yogi, who is
with jaTA. Only parameshvara who wears the gangA, the moon, the snake,
the kapAla, the dhatUra flower etc. has been specifically given the
name kapardI. It is therefore a confirmation that this name refers
only to parameshvara.
Therefore, the name vyuptakesha which comes immediately after kapardi
must also be specific to paramashiva. This name does not appear in
between the names such as the carpenters, potters, fishermen,
outcaste, thieves etc., but instead between those names which refer to
Him as the only one Ishvara who is the Lord of the world. These two
names are mentioned in singular referring to Ishvara only. We have
seen that kapardi is the asAdhAraNa nAma specific to him; therefore
the name vyuptakesha should also be such based on the pattern. This is
an important point we should make note of.
Thus, the name vyuptakesha refers to the form of sannyAsin with shaved
head, which is specific to paramashiva. There is no mUrti other than
our AchArya which can be shown as with a shaven head. Whether it is
dakShiNAmUrti, naTarAja or tripurAri, all these mUrtis are with jaTAs.
When it is so and the veda clearly refers to a particular mUrti of
paramashiva as vyuptakesha, it only refers to the shankara avatAra
which is to take place in the future. This is how abhinava shankara
who has commented on the rudram has explained this nAma.
Will it be enough if we say that when rudram specifically mentions a
person with shaven head as shiva svarUpi, it is specifically our
AchArya? It will be satisfying only if some other authority is also
shown. This is where we examine the purANas. It is the way of our
elders that the meaning of the veda should be understood only through
purANAs and itihAsas.