You only have to worry about the exchange rate really, very little in your upgrade will attract duty now and that won't change in the event of a no deal brexit.
The pound is already really low, historically low, but the full horror of a no deal brexit hasn't been priced in because no sane person considers it possible. If it happened though I'd not be surprised if sterling dropped to about the same as the euro (about a 9% drop). Some articles have suggested parity with the dollar, but that's just project fear
Don't expect big gains if there is a deal, as it's not a 'done deal', just the withdrawal agreement, which mostly just gives us 2 years grace before we've supposed to have negotiated the easiest trade deal in the history of trade deals (hopefully trump loses the election and can come and negotiate it for us).
If article 50 was revoked, with a political consensus for not doing anything so stupid again for a generation, you could see the pound slowly rise up towards $ 1.45. That seems impossible though, the consensus thing I mean. Revoking article 50 will not give huge relief if there's a belief that the Government of the day could collapse and a new lot just throw us under the bus all over again.
I'd recommend you just follow your plans. I doubt anything is going to change this year.