Valve confirmed that the storage on all three Steam Deck models is replaceable for repairable reasons, but stressed that it is only for "people who know what they are doing." [Valve hardware engineer Yazan Aldehayyat told IGN that the SSDs are not soldered to the motherboard and can be replaced or upgraded with the right tools. We use standard M.2 NVMe SSDs," he said. This is a stand-alone module, bucking the trend of mounting directly to the motherboard."

However, this is clearly not Valve's way of encouraging buyers to upgrade casually, but to focus on repairability. Aldehayyat continued, "Repairability is something that we really focus on, and we try to make it as repairable as possible. But this is really for people who know what they're doing and have experience doing it."

How hard could it be? Well, Valve's Pierre-Loup Griffais sheds some light on this point on Discord:

Still, there remains the possibility that buyers who pre-order the $399 model with 64GB of slow eMMC will improve their Steam Deck at a later date. Valve's own spec sheet page states that "all models use socketed 2230 M.2 modules (not intended for end-user replacement)."

However, before you cancel your pre-order, there are several reasons why an upgrade may not be the wisest course of action.

Not only does Valve say that replacing the SSD is for experts, but as Griffais discussed above, cracking a brand new Steam Deck could affect your warranty. Given Nintendo's ongoing issues with Joy Con drifting (Valve is confident that this will not be an issue with the Steam Deck), it may be wise to ensure that the status of the warranty is not in question should other issues arise in the future.

Second, the required M.2 2230 drives are not very popular and are quite expensive at about $200 for 1TB; per GB, not as expensive as Steam Deck's jump from 64GB to 256/512GB, but still the cost of switching / profit analysis is enough to change the price.

Finally, and perhaps most importantly, if you have already secured a 256GB or 512GB Steam Deck this year, you will need to rejoin the last in line to cancel your order and switch to the entry level. Also, if you pre-order the 64GB model today, it is expected to ship "no later than Q2 2022."